Enhanced mobility procedures

ABSTRACT

A wireless device may receive measurement report(s) comprising measurement results associated with a second cell. The wireless device may determine, based on initiating a random access process prior to receiving a cell switch MAC CE, a timing advance value associated with the second cell. The wireless device may receive the cell switch MAC CE indicating switching from a first cell to the second cell. The wireless device may perform an uplink transmission on the second cell based on the timing advance value and in response to receiving the cell switch MAC CE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/290,607, filed Dec. 16, 2021, which is hereby incorporated byreference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B show examples of mobile communications systems inaccordance with several of various embodiments of the presentdisclosure.

FIG. 2A and FIG. 2B show examples of user plane and control planeprotocol layers in accordance with several of various embodiments of thepresent disclosure.

FIG. 3 shows example functions and services offered by protocol layersin a user plane protocol stack in accordance with several of variousembodiments of the present disclosure.

FIG. 4 shows example flow of packets through the protocol layers inaccordance with several of various embodiments of the presentdisclosure.

FIG. 5A shows example mapping of channels between layers of the protocolstack and different physical signals in downlink in accordance withseveral of various embodiments of the present disclosure.

FIG. 5B shows example mapping of channels between layers of the protocolstack and different physical signals in uplink in accordance withseveral of various embodiments of the present disclosure.

FIG. 6 shows example physical layer processes for signal transmission inaccordance with several of various embodiments of the presentdisclosure.

FIG. 7 shows examples of RRC states and RRC state transitions inaccordance with several of various embodiments of the presentdisclosure.

FIG. 8 shows an example time domain transmission structure in NR bygrouping OFDM symbols into slots, subframes and frames in accordancewith several of various embodiments of the present disclosure.

FIG. 9 shows an example of time-frequency resource grid in accordancewith several of various embodiments of the present disclosure.

FIG. 10 shows example adaptation and switching of bandwidth parts inaccordance with several of various embodiments of the presentdisclosure.

FIG. 11A shows example arrangements of carriers in carrier aggregationin accordance with several of various embodiments of the presentdisclosure.

FIG. 11B shows examples of uplink control channel groups in accordancewith several of various embodiments of the present disclosure.

FIG. 12A, FIG. 12B and FIG. 12C show example random access processes inaccordance with several of various embodiments of the presentdisclosure.

FIG. 13A shows example time and frequency structure of SSBs and theirassociations with beams in accordance with several of variousembodiments of the present disclosure.

FIG. 13B shows example time and frequency structure of CSI-RSs and theirassociation with beams in accordance with several of various embodimentsof the present disclosure.

FIG. 14A, FIG. 14B and FIG. 14C show example beam management processesin accordance with several of various embodiments of the presentdisclosure.

FIG. 15 shows example components of a wireless device and a base stationthat are in communication via an air interface in accordance withseveral of various embodiments of the present disclosure.

FIG. 16 shows an example handover process in accordance with several ofvarious embodiments of the present disclosure.

FIG. 17 shows an example medium access control (MAC) control element(CE) in accordance with several of various embodiments of the presentdisclosure.

FIG. 18 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 19 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 20 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 21 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 22 shows an example MAC CE or uplink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 23 shows an example MAC CE or uplink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 24 shows an example MAC CE or uplink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 25 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 26 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 27 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 28 shows an example MAC CE or downlink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 29 shows an example MAC CE or downlink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 30 shows an example MAC CE or downlink control information inaccordance with several of various embodiments of the presentdisclosure.

FIG. 31 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 32 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 33 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 34 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 35 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 36 shows an example process in accordance with several of variousembodiments of the present disclosure.

FIG. 37 shows an example flow diagram in accordance with several ofvarious embodiments of the present disclosure.

FIG. 38 shows an example flow diagram in accordance with several ofvarious embodiments of the present disclosure.

DETAILED DESCRIPTION

The exemplary embodiments of the disclosed technology enhance mobilityprocedures by a wireless device and/or one or more base stations. Theexemplary disclosed embodiments may be implemented in the technicalfield of wireless communication systems. More particularly, theembodiments of the disclosed technology enhance inter-cell mobilityprocedures based on Layer 1/Layer 2 signaling

The devices and/or nodes of the mobile communications system disclosedherein may be implemented based on various technologies and/or variousreleases/versions/amendments of a technology. The various technologiesinclude various releases of long-term evolution (LTE) technologies,various releases of 5G new radio (NR) technologies, various wirelesslocal area networks technologies and/or a combination thereof and/oralike. For example, a base station may support a given technology andmay communicate with wireless devices with different characteristics.The wireless devices may have different categories that define theircapabilities in terms of supporting various features. The wirelessdevice with the same category may have different capabilities. Thewireless devices may support various technologies such as variousreleases of LTE technologies, various releases of 5G NR technologiesand/or a combination thereof and/or alike. At least some of the wirelessdevices in the mobile communications system of the present disclosuremay be stationary or almost stationary. In this disclosure, the terms“mobile communications system” and “wireless communications system” maybe used interchangeably.

FIG. 1A shows an example of a mobile communications system 100 inaccordance with several of various embodiments of the presentdisclosure. The mobile communications system 100 may be, for example,run by a mobile network operator (MNO) or a mobile virtual networkoperator (MVNO). The mobile communications system 100 may be a publicland mobile network (PLMN) run by a network operator providing a varietyof service including voice, data, short messaging service (SMS),multimedia messaging service (MMS), emergency calls, etc. The mobilecommunications system 100 includes a core network (CN) 106, a radioaccess network (RAN) 104 and at least one wireless device 102.

The CN 106 connects the RAN 104 to one or more external networks (e.g.,one or more data networks such as the Internet) and is responsible forfunctions such as authentication, charging and end-to-end connectionestablishment. Several radio access technologies (RATs) may be served bythe same CN 106.

The RAN 104 may implement a RAT and may operate between the at least onewireless device 102 and the CN 106. The RAN 104 may handle radio relatedfunctionalities such as scheduling, radio resource control, modulationand coding, multi-antenna transmissions and retransmission protocols.The wireless device and the RAN may share a portion of the radiospectrum by separating transmissions from the wireless device to the RANand the transmissions from the RAN to the wireless device. The directionof the transmissions from the wireless device to the RAN is known as theuplink and the direction of the transmissions from the RAN to thewireless device is known as the downlink. The separation of uplink anddownlink transmissions may be achieved by employing a duplexingtechnique. Example duplexing techniques include frequency divisionduplexing (FDD), time division duplexing (TDD) or a combination of FDDand TDD.

In this disclosure, the term wireless device may refer to a device thatcommunicates with a network entity or another device using wirelesscommunication techniques. The wireless device may be a mobile device ora non-mobile (e.g., fixed) device. Examples of the wireless deviceinclude cellular phone, smart phone, tablet, laptop computer, wearabledevice (e.g., smart watch, smart shoe, fitness trackers, smart clothing,etc.), wireless sensor, wireless meter, extended reality (XR) devicesincluding augmented reality (AR) and virtual reality (VR) devices,Internet of Things (IoT) device, vehicle to vehicle communicationsdevice, road-side units (RSU), automobile, relay node or any combinationthereof. In some examples, the wireless device (e.g., a smart phone,tablet, etc.) may have an interface (e.g., a graphical user interface(GUI)) for configuration by an end user. In some examples, the wirelessdevice (e.g., a wireless sensor device, etc.) may not have an interfacefor configuration by an end user. The wireless device may be referred toas a user equipment (UE), a mobile station (MS), a subscriber unit, ahandset, an access terminal, a user terminal, a wireless transmit andreceive unit (WTRU) and/or other terminology.

The at least one wireless device may communicate with at least one basestation in the RAN 104. In this disclosure, the term base station mayencompass terminologies associated with various RATs. For example, abase station may be referred to as a Node B in a 3G cellular system suchas Universal Mobile Telecommunication Systems (UMTS), an evolved Node B(eNB) in a 4G cellular system such as evolved universal terrestrialradio access (E-UTRA), a next generation eNB (ng-eNB), a Next GenerationNode B (gNB) in NR and/or a 5G system, an access point (AP) in Wi-Fiand/or other wireless local area networks. A base station may bereferred to as a remote radio head (RRH), a baseband unit (BBU) inconnection with one or more RRHs, a repeater or relay for coverageextension and/or any combination thereof. In some examples, all protocollayers of a base station may be implemented in one unit. In someexamples, some of the protocol layers (e.g., upper layers) of the basestation may be implemented in a first unit (e.g., a central unit (CU))and some other protocol layer (e.g., lower layers) may be implemented inone or more second units (e.g., distributed units (DUs)).

A base station in the RAN 104 includes one or more antennas tocommunicate with the at least one wireless device. The base station maycommunicate with the at least one wireless device using radio frequency(RF) transmissions and receptions via RF transceivers. The base stationantennas may control one or more cells (or sectors). The size and/orradio coverage area of a cell may depend on the range that transmissionsby a wireless device can be successfully received by the base stationwhen the wireless device transmits using the RF frequency of the cell.The base station may be associated with cells of various sizes. At agiven location, the wireless device may be in coverage area of a firstcell of the base station and may not be in coverage area of a secondcell of the base station depending on the sizes of the first cell andthe second cell.

A base station in the RAN 104 may have various implementations. Forexample, a base station may be implemented by connecting a BBU (or a BBUpool) coupled to one or more RRHs and/or one or more relay nodes toextend the cell coverage. The BBU pool may be located at a centralizedsite like a cloud or data center. The BBU pool may be connected to aplurality of RRHs that control a plurality of cells. The combination ofBBU with the one or more RRHs may be referred to as a centralized orcloud RAN (C-RAN) architecture. In some implementations, the BBUfunctions may be implemented on virtual machines (VMs) on servers at acentralized location. This architecture may be referred to as virtualRAN (vRAN). All, most or a portion of the protocol layer functions(e.g., all or portions of physical layer, medium access control (MAC)layer and/or higher layers) may be implemented at the BBU pool and theprocessed data may be transmitted to the RRHs for further processingand/or RF transmission. The links between the BBU pool and the RRHs maybe referred to as fronthaul.

In some deployment scenarios, the RAN 104 may include macrocell basestations with high transmission power levels and large coverage areas.In other deployment scenarios, the RAN 104 may include base stationsthat employ different transmission power levels and/or have cells withdifferent coverage areas. For example, some base station may bemacrocell base stations with high transmission powers and/or largecoverage areas and other base station may be small cell base stationswith comparatively smaller transmission powers and/or coverage areas. Insome deployment scenarios, a small cell base station may have coveragethat is within or has overlap with coverage area of a macrocell basestation. A wireless device may communicate with the macrocell basestation while within the coverage area of the macrocell base station.For additional capacity, the wireless device may communicate with boththe macrocell base station and the small cell base station while in theoverlapped coverage area of the macrocell base station and the smallcell base station. Depending on their coverage areas, a small cell basestation may be referred to as a microcell base station, a picocell basestation, a femtocell base station or a home base station.

Different standard development organizations (SDOs) have specified, ormay specify in future, mobile communications systems that have similarcharacteristics as the mobile communications system 100 of FIG. 1A. Forexample, the Third-Generation Partnership Project (3GPP) is a group ofSDOs that provides specifications that define 3GPP technologies formobile communications systems that are akin to the mobile communicationssystem 100. The 3GPP has developed specifications for third generation(3G) mobile networks, fourth generation (4G) mobile networks and fifthgeneration (5G) mobile networks. The 3G, 4G and 5G networks are alsoknown as Universal Mobile Telecommunications System (UMTS), Long TermEvolution (LTE) and 5G system (5GS), respectively. In this disclosure,embodiments are described with respect to the RAN implemented in a 3GPP5G mobile network that is also referred to as next generation RAN(NG-RAN). The embodiments may also be implemented in other mobilecommunications systems such as 3G or 4G mobile networks or mobilenetworks that may be standardized in future such as sixth generation(6G) mobile networks or mobile networks that are implemented bystandards bodies other than 3GPP. The NG-RAN may be based on a new RATknown as new radio (NR) and/or other radio access technologies such asLTE and/or non-3GPP RATs.

FIG. 1B shows an example of a mobile communications system 110 inaccordance with several of various embodiments of the presentdisclosure. The mobile communications system 110 of FIG. 1B is anexample of a 5G mobile network and includes a 5G CN (5G-CN) 130, anNG-RAN 120 and UEs (collectively 112 and individually UE 112A and UE112B). The 5G-CN 130, the NG-RAN 120 and the UEs 112 of FIG. 1B operatesubstantially alike the CN 106, the RAN 104 and the at least onewireless device 102, respectively, as described for FIG. 1A.

The 5G-CN 130 of FIG. 1B connects the NG-RAN 120 to one or more externalnetworks (e.g., one or more data networks such as the Internet) and isresponsible for functions such as authentication, charging andend-to-end connection establishment. The 5G-CN has new enhancementscompared to previous generations of CNs (e.g., evolved packet core (EPC)in the 4G networks) including service-based architecture, support fornetwork slicing and control plane/user plane split. The service-basedarchitecture of the 5G-CN provides a modular framework based on serviceand functionalities provided by the core network wherein a set ofnetwork functions are connected via service-based interfaces. Thenetwork slicing enables multiplexing of independent logical networks(e.g., network slices) on the same physical network infrastructure. Forexample, a network slice may be for mobile broadband applications withfull mobility support and a different network slice may be fornon-mobile latency-critical applications such as industry automation.The control plane/user plane split enables independent scaling of thecontrol plane and the user plane. For example, the control planecapacity may be increased without affecting the user plane of thenetwork.

The 5G-CN 130 of FIG. 1B includes an access and mobility managementfunction (AMF) 132 and a user plane function (UPF) 134. The AMF 132 maysupport termination of non-access stratum (NAS) signaling, NAS signalingsecurity such as ciphering and integrity protection, inter-3GPP accessnetwork mobility, registration management, connection management,mobility management, access authentication and authorization andsecurity context management. The NAS is a functional layer between a UEand the CN and the access stratum (AS) is a functional layer between theUE and the RAN. The UPF 134 may serve as an interconnect point betweenthe NG-RAN and an external data network. The UPF may support packetrouting and forwarding, packet inspection and Quality of Service (QoS)handling and packet filtering. The UPF may further act as a ProtocolData Unit (PDU) session anchor point for mobility within and betweenRATs.

The 5G-CN 130 may include additional network functions (not shown inFIG. 1B) such as one or more Session Management Functions (SMFs), aPolicy Control Function (PCF), a Network Exposure Function (NEF), aUnified Data Management (UDM), an Application Function (AF), and/or anAuthentication Server Function (AUSF). These network functions alongwith the AMF 132 and UPF 134 enable a service-based architecture for the5G-CN.

The NG-RAN 120 may operate between the UEs 112 and the 5G-CN 130 and mayimplement one or more RATs. The NG-RAN 120 may include one or more gNBs(e.g., gNB 122A or gNB 122B or collectively gNBs 122) and/or one or moreng-eNBs (e.g., ng-eNB 124A or ng-eNB 124B or collectively ng-eNBs 124).The general terminology for gNBs 122 and/or an ng-eNBs 124 is a basestation and may be used interchangeably in this disclosure. The gNBs 122and the ng-eNBs 124 may include one or more antennas to communicate withthe UEs 112. The one or more antennas of the gNBs 122 or ng-eNBs 124 maycontrol one or more cells (or sectors) that provide radio coverage forthe UEs 112.

A gNB and/or an ng-eNB of FIG. 1B may be connected to the 5G-CN 130using an NG interface. A gNB and/or an ng-eNB may be connected withother gNBs and/or ng-eNBs using an Xn interface. The NG or the Xninterfaces are logical connections that may be established using anunderlying transport network. The interface between a UE and a gNB orbetween a UE and an ng-eNBs may be referred to as the Uu interface. Aninterface (e.g., Uu, NG or Xn) may be established by using a protocolstack that enables data and control signaling exchange between entitiesin the mobile communications system of FIG. 1B. When a protocol stack isused for transmission of user data, the protocol stack may be referredto as user plane protocol stack. When a protocol stack is used fortransmission of control signaling, the protocol stack may be referred toas control plane protocol stack. Some protocol layer may be used in bothof the user plane protocol stack and the control plane protocol stackwhile other protocol layers may be specific to the user plane or controlplane.

The NG interface of FIG. 1B may include an NG-User plane (NG-U)interface between a gNB and the UPF 134 (or an ng-eNB and the UPF 134)and an NG-Control plane (NG-C) interface between a gNB and the AMF 132(or an ng-eNB and the AMF 132). The NG-U interface may providenon-guaranteed delivery of user plane PDUs between a gNB and the UPF oran ng-eNB and the UPF. The NG-C interface may provide services such asNG interface management, UE context management, UE mobility management,transport of NAS messages, paging, PDU session management, configurationtransfer and/or warning message transmission.

The UEs 112 and a gNB may be connected using the Uu interface and usingthe NR user plane and control plane protocol stack. The UEs 112 and anng-eNB may be connected using the Uu interface using the LTE user planeand control plane protocol stack.

In the example mobile communications system of FIG. 1B, a 5G-CN isconnected to a RAN comprised of 4G LTE and/or 5G NR RATs. In otherexample mobile communications systems, a RAN based on the 5G NR RAT maybe connected to a 4G CN (e.g., EPC). For example, earlier releases of 5Gstandards may support a non-standalone mode of operation where a NRbased RAN is connected to the 4G EPC. In an example non-standalone mode,a UE may be connected to both a NR gNB and a 4G LTE eNB (e.g., a ng-eNB)and the control plane functionalities (such as initial access, pagingand mobility) may be provided through the 4G LTE eNB. In a standalone ofoperation, the 5G NR gNB is connected to a 5G-CN and the user plane andthe control plane functionalities are provided by the 5G NR gNB.

FIG. 2A shows an example of the protocol stack for the user plan of anNR Uu interface in accordance with several of various embodiments of thepresent disclosure. The user plane protocol stack comprises fiveprotocol layers that terminate at the UE 200 and the gNB 210. The fiveprotocol layers, as shown in FIG. 2A, include physical (PHY) layerreferred to as PHY 201 at the UE 200 and PHY 211 at the gNB 210, mediumaccess control (MAC) layer referred to as MAC 202 at the UE 200 and MAC212 at the gNB 210, radio link control (RLC) layer referred to as RLC203 at the UE 200 and RLC 213 at the gNB 210, packet data convergenceprotocol (PDCP) layer referred to as PDCP 204 at the UE 200 and PDCP 214at the gNB 210, and service data application protocol (SDAP) layerreferred to as SDAP 205 at the UE 200 and SDAP 215 at the gNB 210. ThePHY layer, also known as layer 1 (L1), offers transport services tohigher layers. The other four layers of the protocol stack (MAC, RLC,PDCP and SDAP) are collectively known as layer 2 (L2).

FIG. 2B shows an example of the protocol stack for the control plan ofan NR Uu interface in accordance with several of various embodiments ofthe present disclosure. Some of the protocol layers (PHY, MAC, RLC andPDCP) are common between the user plane protocol stack shown in FIG. 2Aand the control plan protocol stack. The control plane protocol stackalso includes the RRC layer, referred to RRC 206 at the UE 200 and RRC216 at the gNB 210, that also terminates at the UE 200 and the gNB 210.In addition, the control plane protocol stack includes the NAS layerthat terminates at the UE 200 and the AMF 220. In FIG. 2B, the NAS layeris referred to as NAS 207 at the UE 200 and NAS 227 at the AMF 220.

FIG. 3 shows example functions and services offered to other layers by alayer in the NR user plane protocol stack of FIG. 2A in accordance withseveral of various embodiments of the present disclosure. For example,the SDAP layer of FIG. 3 (shown in FIG. 2A as SDAP 205 at the UE sideand SDAP 215 at the gNB side) may perform mapping and de-mapping of QoSflows to data radio bearers. The mapping and de-mapping may be based onQoS (e.g., delay, throughput, jitter, error rate, etc.) associated witha QoS flow. A QoS flow may be a QoS differentiation granularity for aPDU session which is a logical connection between a UE 200 and a datanetwork. A PDU session may contain one or more QoS flows. The functionsand services of the SDAP layer include mapping and de-mapping betweenone or more QoS flows and one or more data radio bearers. The SDAP layermay also mark the uplink and/or downlink packets with a QoS flow ID(QFI).

The PDCP layer of FIG. 3 (shown in FIG. 2A as PDCP 204 at the UE sideand PDCP 214 at the gNB side) may perform header compression anddecompression (e.g., using Robust Header Compression (ROHC) protocol) toreduce the protocol header overhead, ciphering and deciphering andintegrity protection and verification to enhance the security over theair interface, reordering and in-order delivery of packets anddiscarding of duplicate packets. A UE may be configured with one PDCPentity per bearer.

In an example scenario not shown in FIG. 3 , a UE may be configured withdual connectivity and may connect to two different cell groups providedby two different base stations. For example, a base station of the twobase stations may be referred to as a master base station and a cellgroup provided by the master base station may be referred to as a mastercell group (MCG). The other base station of the two base stations may bereferred to as a secondary base station and the cell group provided bythe secondary base station may be referred to as a secondary cell group(SCG). A bearer may be configured for the UE as a split bearer that maybe handled by the two different cell groups. The PDCP layer may performrouting of packets corresponding to a split bearer to and/or from RLCchannels associated with the cell groups.

In an example scenario not shown in FIG. 3 , a bearer of the UE may beconfigured (e.g., with control signaling) with PDCP packet duplication.A bearer configured with PDCP duplication may be mapped to a pluralityof RLC channels each corresponding to different one or more cells. ThePDCP layer may duplicate packets of the bearer configured with PDCPduplication and the duplicated packets may be mapped to the differentRLC channels. With PDCP packet duplication, the likelihood of correctreception of packets increases thereby enabling higher reliability.

The RLC layer of FIG. 3 (shown in FIG. 2A as RLC 203 at the UE side andRLC 213 at the gNB side) provides service to upper layers in the form ofRLC channels. The RLC layer may include three transmission modes:transparent mode (TM), Unacknowledged mode (UM) and Acknowledged mode(AM). The RLC layer may perform error correction through automaticrepeat request (ARQ) for the AM transmission mode, segmentation of RLCservice data units (SDUs) for the AM and UM transmission modes andre-segmentation of RLC SDUs for AM transmission mode, duplicatedetection for the AM transmission mode, RLC SDU discard for the AM andUM transmission modes, etc. The UE may be configured with one RLC entityper RLC channel.

The MAC layer of FIG. 3 (shown in FIG. 2A as MAC 202 at the UE side andMAC 212 at the gNB side) provides services to the RLC layer in form oflogical channels. The MAC layer may perform mapping between logicalchannels and transport channels, multiplexing/demultiplexing of MAC SDUsbelonging to one or more logical channels into/from transport blocks (TBs) delivered to/from the physical layer on transport channels, reportingof scheduling information, error correction through hybrid automaticrepeat request (HARQ), priority handling between UEs by means of dynamicscheduling, priority handling between logical channels of one UE bymeans of logical channel prioritization and/or padding. In case ofcarrier aggregation, a MAC entity may comprise one HARQ entity per cell.A MAC entity may support multiple numerologies, transmission timings andcells. The control signaling may configure logical channels with mappingrestrictions. The mapping restrictions in logical channel prioritizationmay control the numerology(ies), cell(s), and/or transmissiontiming(s)/duration(s) that a logical channel may use.

The PHY layer of FIG. 3 (shown in FIG. 2A as PHY 201 at the UE side andPHY 211 at the gNB side) provides transport services to the MAC layer inform of transport channels. The physical layer may handlecoding/decoding, HARQ soft combining, rate matching of a coded transportchannel to physical channels, mapping of coded transport channels tophysical channels, modulation and demodulation of physical channels,frequency and time synchronization, radio characteristics measurementsand indication to higher layers, RF processing, and mapping to antennasand radio resources.

FIG. 4 shows example processing of packets at different protocol layersin accordance with several of various embodiments of the presentdisclosure. In this example, three Internet Protocol (IP) packets thatare processed by the different layers of the NR protocol stack. The termSDU shown in FIG. 4 is the data unit that is entered from/to a higherlayer. In contrast, a protocol data unit (PDU) is the data unit that isentered to/from a lower layer. The flow of packets in FIG. 4 is fordownlink. An uplink data flow through layers of the NR protocol stack issimilar to FIG. 4 . In this example, the two leftmost IP packets aremapped by the SDAP layer (shown as SDAP 205 and SDAP 215 in FIG. 2A) toradio bearer 402 and the rightmost packet is mapped by the SDAP layer tothe radio bearer 404. The SDAP layer adds SDAP headers to the IP packetswhich are entered into the PDCP layer as PDCP SDUs. The PDCP layer isshown as PDCP 204 and PDCP 214 in FIG. 2A. The PDCP layer adds the PDCPheaders to the PDCP SDUs which are entered into the RLC layer as RLCSDUs. The RLC layer is shown as RLC 203 and RLC 213 in FIG. 2A. An RLCSDU may be segmented at the RLC layer. The RLC layer adds RLC headers tothe RLC SDUs after segmentation (if segmented) which are entered intothe MAC layer as MAC SDUs. The MAC layer adds the MAC headers to the MACSDUs and multiplexes one or more MAC SDUs to form a PHY SDU (alsoreferred to as a transport block (TB) or a MAC PDU).

In FIG. 4 , the MAC SDUs are multiplexed to form a transport block. TheMAC layer may multiplex one or more MAC control elements (MAC CEs) withzero or more MAC SDUs to form a transport block. The MAC CEs may also bereferred to as MAC commands or MAC layer control signaling and may beused for in-band control signaling. The MAC CEs may be transmitted by abase station to a UE (e.g., downlink MAC CEs) or by a UE to a basestation (e.g., uplink MAC CEs). The MAC CEs may be used for transmissionof information useful by a gNB for scheduling (e.g., buffer statusreport (BSR) or power headroom report (PHR)), activation/deactivation ofone or more cells, activation/deactivation of configured radio resourcesfor or one or more processes, activation/deactivation of one or moreprocesses, indication of parameters used in one or more processes, etc.

FIG. 5A and FIG. 5B show example mapping between logical channels,transport channels and physical channels for downlink and uplink,respectively in accordance with several of various embodiments of thepresent disclosure. As discussed before, the MAC layer provides servicesto higher layer in the form of logical channels. A logical channel maybe classified as a control channel, if used for transmission of controland/or configuration information, or a traffic channel if used fortransmission of user data. Example logical channels in NR includeBroadcast Control Channel (BCCH) used for transmission of broadcastsystem control information, Paging Control Channel (PCCH) used forcarrying paging messages for wireless devices with unknown locations,Common Control Channel (CCCH) used for transmission of controlinformation between UEs and network and for UEs that have no RRCconnection with the network, Dedicated Control Channel (DCCH) which is apoint-to-point bi-directional channel for transmission of dedicatedcontrol information between a UE that has an RRC connection and thenetwork and Dedicated Traffic Channel (DTCH) which is point-to-pointchannel, dedicated to one UE, for the transfer of user information andmay exist in both uplink and downlink.

As discussed before, the PHY layer provides services to the MAC layerand higher layers in the form of transport channels. Example transportchannels in NR include Broadcast Channel (BCH) used for transmission ofpart of the BCCH referred to as master information block (MIB), DownlinkShared Channel (DL-SCH) used for transmission of data (e.g., from DTCHin downlink) and various control information (e.g., from DCCH and CCCHin downlink and part of the BCCH that is not mapped to the BCH), UplinkShared Channel (UL-SCH) used for transmission of uplink data (e.g., fromDTCH in uplink) and control information (e.g., from CCCH and DCCH inuplink) and Paging Channel (PCH) used for transmission of paginginformation from the PCCH. In addition, Random Access Channel (RACH) isa transport channel used for transmission of random access preambles.The RACH does not carry a transport block. Data on a transport channel(except RACH) may be organized in transport blocks, wherein One or moretransport blocks may be transmitted in a transmission time interval(TTI).

The PHY layer may map the transport channels to physical channels. Aphysical channel may correspond to time-frequency resources that areused for transmission of information from one or more transportchannels. In addition to mapping transport channels to physicalchannels, the physical layer may generate control information (e.g.,downlink control information (DCI) or uplink control information (UCI))that may be carried by the physical channels. Example DCI includescheduling information (e.g., downlink assignments and uplink grants),request for channel state information report, power control command,etc. Example UCI include HARQ feedback indicating correct or incorrectreception of downlink transport blocks, channel state informationreport, scheduling request, etc. Example physical channels in NR includea Physical Broadcast Channel (PBCH) for carrying information from theBCH, a Physical Downlink Shared Channel (PDSCH) for carrying informationform the PCH and the DL-SCH, a Physical Downlink Control Channel (PDCCH)for carrying DCI, a Physical Uplink Shared Channel (PUSCH) for carryinginformation from the UL-SCH and/or UCI, a Physical Uplink ControlChannel (PUCCH) for carrying UCI and Physical Random Access Channel(PRACH) for transmission of RACH (e.g., random access preamble).

The PHY layer may also generate physical signals that are not originatedfrom higher layers. As shown in FIG. 5A, example downlink physicalsignals include Demodulation Reference Signal (DM-RS), Phase TrackingReference Signal (PT-RS), Channel State Information Reference Signal(CSI-RS), Primary Synchronization Signal (PSS) and SecondarySynchronization Signal (SSS). As shown in FIG. 5B, example uplinkphysical signals include DM-RS, PT-RS and sounding reference signal(SRS).

As indicated earlier, some of the protocol layers (PHY, MAC, RLC andPDCP) of the control plane of an NR Uu interface, are common between theuser plane protocol stack (as shown in FIG. 2A) and the control planeprotocol stack (as shown in FIG. 2B). In addition to PHY, MAC, RLC andPDCP, the control plane protocol stack includes the RRC protocol layerand the NAS protocol layer.

The NAS layer, as shown in FIG. 2B, terminates at the UE 200 and the AMF220 entity of the 5G-C 130. The NAS layer is used for core networkrelated functions and signaling including registration, authentication,location update and session management. The NAS layer uses services fromthe AS of the Uu interface to transmit the NAS messages.

The RRC layer, as shown in FIG. 2B, operates between the UE 200 and thegNB 210 (more generally NG-RAN 120) and may provide services andfunctions such as broadcast of system information (SI) related to AS andNAS as well as paging initiated by the 5G-C 130 or NG-RAN 120. Inaddition, the RRC layer is responsible for establishment, maintenanceand release of an RRC connection between the UE 200 and the NG-RAN 120,carrier aggregation configuration (e.g., addition, modification andrelease), dual connectivity configuration (e.g., addition, modificationand release), security related functions, radio bearerconfiguration/maintenance and release, mobility management (e.g.,maintenance and context transfer), UE cell selection and reselection,inter-RAT mobility, QoS management functions, UE measurement reportingand control, radio link failure (RLF) detection and NAS messagetransfer. The RRC layer uses services from PHY, MAC, RLC and PDCP layersto transmit RRC messages using signaling radio bearers (SRBs). The SRBsare mapped to CCCH logical channel during connection establishment andto DCCH logical channel after connection establishment.

FIG. 6 shows example physical layer processes for signal transmission inaccordance with several of various embodiments of the presentdisclosure. Data and/or control streams from MAC layer may beencoded/decoded to offer transport and control services over the radiotransmission link. For example, one or more (e.g., two as shown in FIG.6 ) transport blocks may be received from the MAC layer for transmissionvia a physical channel (e.g., a physical downlink shared channel or aphysical uplink shared channel). A cyclic redundancy check (CRC) may becalculated and attached to a transport block in the physical layer. TheCRC calculation may be based on one or more cyclic generatorpolynomials. The CRC may be used by the receiver for error detection.Following the transport block CRC attachment, a low-density parity check(LDPC) base graph selection may be performed. In example embodiments,two LDPC base graphs may be used wherein a first LDPC base graph may beoptimized for small transport blocks and a second LDPC base graph may beoptimized for comparatively larger transport blocks.

The transport block may be segmented into code blocks and code block CRCmay be calculated and attached to a code block. A code block may be LDPCcoded and the LDPC coded blocks may be individually rate matched. Thecode blocks may be concatenated to create one or more codewords. Thecontents of a codeword may be scrambled and modulated to generate ablock of complex-valued modulation symbols. The modulation symbols maybe mapped to a plurality of transmission layers (e.g., multiple-inputmultiple-output (MIMO) layers) and the transmission layers may besubject to transform precoding and/or precoding. The precodedcomplex-valued symbols may be mapped to radio resources (e.g., resourceelements). The signal generator block may create a baseband signal andup-convert the baseband signal to a carrier frequency for transmissionvia antenna ports. The signal generator block may employ mixers, filtersand/or other radio frequency (RF) components prior to transmission viathe antennas. The functions and blocks in FIG. 6 are illustrated asexamples and other mechanisms may be implemented in various embodiments.

FIG. 7 shows examples of RRC states and RRC state transitions at a UE inaccordance with several of various embodiments of the presentdisclosure. A UE may be in one of three RRC states: RRC_IDLE 702, RRCINACTIVE 704 and RRC_CONNECTED 706. In RRC_IDLE 702 state, no RRCcontext (e.g., parameters needed for communications between the UE andthe network) may be established for the UE in the RAN. In RRC_IDLE 702state, no data transfer between the UE and the network may take placeand uplink synchronization is not maintained. The wireless device maysleep most of the time and may wake up periodically to receive pagingmessages. The uplink transmission of the UE may be based on a randomaccess process and to enable transition to the RRC_CONNECTED 706 state.The mobility in RRC_IDLE 702 state is through a cell reselectionprocedure where the UE camps on a cell based on one or more criteriaincluding signal strength that is determined based on the UEmeasurements.

In RRC_CONNECTED 706 state, the RRC context is established and both theUE and the RAN have necessary parameters to enable communicationsbetween the UE and the network. In the RRC_CONNECTED 706 state, the UEis configured with an identity known as a Cell Radio Network TemporaryIdentifier (C-RNTI) that is used for signaling purposes (e.g., uplinkand downlink scheduling, etc.) between the UE and the RAN. The wirelessdevice mobility in the RRC_CONNECTED 706 state is managed by the RAN.The wireless device provides neighboring cells and/or current servingcell measurements to the network and the network may make hand overdecisions. Based on the wireless device measurements, the currentserving base station may send a handover request message to aneighboring base station and may send a handover command to the wirelessdevice to handover to a cell of the neighboring base station. Thetransition of the wireless device from the RRC_IDLE 702 state to theRRC_CONNECTED 706 state or from the RRC_CONNECTED 706 state to theRRC_IDLE 702 state may be based on connection establishment andconnection release procedures (shown collectively as connectionestablishment/release 710 in FIG. 7 ).

To enable a faster transition to the RRC_CONNECTED 706 state (e.g.,compared to transition from RRC_IDLE 702 state to RRC_CONNECTED 706state), an RRC_INACTIVE 704 state is used for an NR UE wherein, the RRCcontext is kept at the UE and the RAN. The transition from theRRC_INACTIVE 704 state to the RRC_CONNECTED 706 state is handled by RANwithout CN signaling. Similar to the RRC_IDLE 702 state, the mobility inRRC_INACTIVE 704 state is based on a cell reselection procedure withoutinvolvement from the network. The transition of the wireless device fromthe RRC_INACTIVE 704 state to the RRC_CONNECTED 706 state or from theRRC_CONNECTED 706 state to the RRC_INACTIVE 704 state may be based onconnection resume and connection inactivation procedures (showncollectively as connection resume/inactivation 712 in FIG. 7 ). Thetransition of the wireless device from the RRC_INACTIVE 704 state to theRRC_IDLE 702 state may be based on a connection release 714 procedure asshown in FIG. 7 .

In NR, Orthogonal Frequency Division Multiplexing (OFDM), also calledcyclic prefix OFDM (CP-OFDM), is the baseline transmission scheme inboth downlink and uplink of NR and the Discrete Fourier Transform (DFT)spread OFDM (DFT-s-OFDM) is a complementary uplink transmission inaddition to the baseline OFDM scheme. OFDM is multi-carrier transmissionscheme wherein the transmission bandwidth may be composed of severalnarrowband sub-carriers. The subcarriers are modulated by the complexvalued OFDM modulation symbols resulting in an OFDM signal. The complexvalued OFDM modulation symbols are obtained by mapping, by a modulationmapper, the input data (e.g., binary digits) to different points of amodulation constellation diagram. The modulation constellation diagramdepends on the modulation scheme. NR may use different types ofmodulation schemes including Binary Phase Shift Keying (BPSK), π/2-BPSK,Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation(16QAM), 64QAM and 256QAM. Different and/or higher order modulationschemes (e.g., M-QAM in general) may be used. An OFDM signal with Nsubcarriers may be generated by processing N subcarriers in parallel forexample by using Inverse Fast Fourier Transform (IFFT) processing. TheOFDM receiver may use FFT processing to recover the transmitted OFDMmodulation symbols. The subcarrier spacing of subcarriers in an OFDMsignal is inversely proportional to an OFDM modulation symbol duration.For example, for a 15 KHz subcarrier spacing, duration of an OFDM signalis nearly 66.7 μs. To enhance the robustness of OFDM transmission intime dispersive channels, a cyclic prefix (CP) may be inserted at thebeginning of an OFDM symbol. For example, the last part of an OFDMsymbol may be copied and inserted at the beginning of an OFDM symbol.The CP insertion enhanced the OFDM transmission scheme by preservingsubcarrier orthogonality in time dispersive channels.

In NR, different numerologies may be used for OFDM transmission. Anumerology of OFDM transmission may indicate a subcarrier spacing and aCP duration for the OFDM transmission. For example, a subcarrier spacingin NR may generally be a multiple of 15 KHz and expressed as Δf=2^(μ)·15KHz (μ=0, 1, 2, . . . ). Example subcarrier spacings used in NR include15 KHz (μ=0), 30 KHz (μ=1), 60 KHz (μ=2), 120 KHz (μ=3) and 240 KHz(μ=4). As discussed before, a duration of OFDM symbol is inverselyproportional to the subcarrier spacing and therefor OFDM symbol durationmay depend on the numerology (e.g., the μ value).

FIG. 8 shows an example time domain transmission structure in NR whereinOFDM symbols are grouped into slots, subframes and frames in accordancewith several of various embodiments of the present disclosure. A slot isa group of N_(symb) ^(slot) OFDM symbols, wherein the N_(symb) ^(slot)may have a constant value (e.g., 14). Since different numerologiesresults in different OFDM symbol durations, duration of a slot may alsodepend on the numerology and may be variable. A subframe may have aduration of 1 ms and may be composed of one or more slots, the number ofwhich may depend on the slot duration. The number of slots per subframeis therefore a function of μ and may generally expressed as N_(slot)^(subframe,μ) and the number of symbols per subframe may be expressed asN_(symb) ^(subframe,μ)=N_(symb) ^(slot)N_(slot) ^(subframe,μ). A mayhave a duration of 10 ms and may consist of 10 subframes. The number ofslots per frame may depend on the numerology and therefore may bevariable. The number of slots per frame may generally be expressed asN_(slot) ^(frame,μ).

An antenna port may be defined as a logical entity such that channelcharacteristics over which a symbol on the antenna port is conveyed maybe inferred from the channel characteristics over which another symbolon the same antenna port is conveyed. For example, for DM-RS associatedwith a PDSCH, the channel over which a PDSCH symbol on an antenna portis conveyed may be inferred from the channel over which a DM-RS symbolon the same antenna port is conveyed, for example, if the two symbolsare within the same resource as the scheduled PDSCH and/or in the sameslot and/or in the same precoding resource block group (PRG). Forexample, for DM-RS associated with a PDCCH, the channel over which aPDCCH symbol on an antenna port is conveyed may be inferred from thechannel over which a DM-RS symbol on the same antenna port is conveyedif, for example, the two symbols are within resources for which the UEmay assume the same precoding being used. For example, for DM-RSassociated with a PBCH, the channel over which a PBCH symbol on oneantenna port is conveyed may be inferred from the channel over which aDM-RS symbol on the same antenna port is conveyed if, for example, thetwo symbols are within a SS/PBCH block transmitted within the same slot,and with the same block index. The antenna port may be different from aphysical antenna. An antenna port may be associated with an antenna portnumber and different physical channels may correspond to differentranges of antenna port numbers.

FIG. 9 shows an example of time-frequency resource grid in accordancewith several of various embodiments of the present disclosure. Thenumber of subcarriers in a carrier bandwidth may be based on thenumerology of OFDM transmissions in the carrier. A resource element,corresponding to one symbol duration and one subcarrier, may be thesmallest physical resource in the time-frequency grid. A resourceelement (RE) for antenna port p and subcarrier spacing configuration μmay be uniquely identified by (k,l)_(p,u) where k is the index of asubcarrier in the frequency domain and l may refer to the symbolposition in the time domain relative to some reference point. A resourceblock may be defined as N_(SC) ^(RB)=12 subcarriers. Since subcarrierspacing depends on the numerology of OFDM transmission, the frequencydomain span of a resource block may be variable and may depend on thenumerology. For example, for a subcarrier spacing of 15 KHz (e.g., μ=0),a resource block may be 180 KHz and for a subcarrier spacing of 30 KHz(e.g., μ=1), a resource block may be 360 KHz.

With large carrier bandwidths defined in NR and due to limitedcapabilities for some UEs (e.g., due to hardware limitations), a UE maynot support an entire carrier bandwidth. Receiving on the full carrierbandwidth may imply high energy consumption. For example, transmittingdownlink control channels on the full downlink carrier bandwidth mayresult in high power consumption for wide carrier bandwidths. NR may usea bandwidth adaptation procedure to dynamically adapt the transmit andreceive bandwidths. The transmit and receive bandwidth of a UE on a cellmay be smaller than the bandwidth of the cell and may be adjusted. Forexample, the width of the transmit and/or receive bandwidth may change(e.g., shrink during period of low activity to save power); the locationof the transmit and/or receive bandwidth may move in the frequencydomain (e.g., to increase scheduling flexibility); and the subcarrierspacing of the transmit or receive bandwidth may change (e.g., to allowdifferent services). A subset of the cell bandwidth may be referred toas a Bandwidth Part (BWP) and bandwidth adaptation may be achieved byconfiguring the UE with one or more BWPs. The base station may configurea UE with a set of downlink BWPs and a set of uplink BWPs. A BWP may becharacterized by a numerology (e.g., subcarrier spacing and cyclicprefix) and a set of consecutive resource blocks in the numerology ofthe BWP. One or more first BWPs of the one or more BWPs of the cell maybe active at a time. An active BWP may be an active downlink BWP or anactive uplink BWP.

FIG. 10 shows an example of bandwidth part adaptation and switching. Inthis example, three BWPs (BWP₁ 1004, BWP₂ 1006 and BWP₃ 1008) areconfigured for a UE on a carrier bandwidth. The BWP₁ is configured witha bandwidth of 40 MHz and a numerology with subcarrier spacing of 15KHz, the BWP₂ is configured with a bandwidth of 10 MHz and a numerologywith subcarrier spacing of 15 KHz and the BWP₃ is configured with abandwidth of 20 MHz and a subcarrier spacing of 60 KHz. The wirelessdevice may switch from a first BWP (e.g., BWP₁) to a second BWP (e.g.,BWP₂). An active BWP of the cell may change from the first BWP to thesecond BWP in response to the BWP switching.

The BWP switching (e.g., BWP switching 1010, BWP switching 1012, BWPswitching 1014, or BWP switching 1016 in FIG. 10 ) may be based on acommand from the base station. The command may be a DCI comprisingscheduling information for the UE in the second BWP. In case of uplinkBWP switching, the first BWP and the second BWP may be uplink BWPs andthe scheduling information may be an uplink grant for uplinktransmission via the second BWP. In case of downlink BWP switching, thefirst BWP and the second BWP may be downlink BWPs and the schedulinginformation may be a downlink assignment for downlink reception via thesecond BWP.

The BWP switching (e.g., BWP switching 1010, BWP switching 1012, BWPswitching 1014, or BWP switching 1016 in FIG. 10 ) may be based on anexpiry of a timer. The base station may configure a wireless device witha BWP inactivity timer and the wireless device may switch to a defaultBWP (e.g., default downlink BWP) based on the expiry of the BWPinactivity timer. The expiry of the BWP inactivity timer may be anindication of low activity on the current active downlink BWP. The basestation may configure the wireless device with the default downlink BWP.If the base station does not configure the wireless device with thedefault BWP, the default BWP may be an initial downlink BWP. The initialactive BWP may be the BWP that the wireless device receives schedulinginformation for remaining system information upon transition to anRRC_CONNECTED state.

A wireless device may monitor a downlink control channel of a downlinkBWP. For example, the UE may monitor a set of PDCCH candidates inconfigured monitoring occasions in one or more configured COntrolREsource SETs (CORESETs) according to the corresponding search spaceconfigurations. A search space configuration may define how/where tosearch for PDCCH candidates. For example, the search space configurationparameters may comprise a monitoring periodicity and offset parameterindicating the slots for monitoring the PDCCH candidates. The searchspace configuration parameters may further comprise a parameterindicating a first symbol with a slot within the slots determined formonitoring PDCCH candidates. A search space may be associated with oneor more CORESETs and the search space configuration may indicate one ormore identifiers of the one or more CORESETs. The search spaceconfiguration parameters may further indicate that whether the searchspace is a common search space or a UE-specific search space. A commonsearch space may be monitored by a plurality of wireless devices and aUE-specific search space may be dedicated to a specific UE.

FIG. 11A shows example arrangements of carriers in carrier aggregationin accordance with several of various embodiments of the presentdisclosure. With carrier aggregation, multiple NR component carriers(CCs) may be aggregated. Downlink transmissions to a wireless device maytake place simultaneously on the aggregated downlink CCs resulting inhigher downlink data rates. Uplink transmissions from a wireless devicemay take place simultaneously on the aggregated uplink CCs resulting inhigher uplink data rates. The component carriers in carrier aggregationmay be on the same frequency band (e.g., intra-band carrier aggregation)or on different frequency bands (e.g., inter-band carrier aggregation).The component carriers may also be contiguous or non-contiguous. Thisresults in three possible carrier aggregation scenarios, intra-bandcontiguous CA 1102, intra-band non-contiguous CA 1104 and inter-band CA1106 as shown in FIG. 11A. Depending on the UE capability for carrieraggregation, a UE may transmit and/or receive on multiple carriers orfor a UE that is not capable of carrier aggregation, the UE may transmitand/or receive on one component carrier at a time. In this disclosure,the carrier aggregation is described using the term cell and a carrieraggregation capable UE may transmit and/or receive via multiple cells.

In carrier aggregation, a UE may be configured with multiple cells. Acell of the multiple cells configured for the UE may be referred to as aPrimary Cell (PCell). The PCell may be the first cell that the UE isinitially connected to. One or more other cells configured for the UEmay be referred to as Secondary Cells (SCells). The base station mayconfigure a UE with multiple SCells. The configured SCells may bedeactivated upon configuration and the base station may dynamicallyactivate or deactivate one or more of the configured SCells based ontraffic and/or channel conditions. The base station may activate ordeactivate configured SCells using a SCell Activation/Deactivation MACCE. The SCell Activation/Deactivation MAC CE may comprise a bitmap,wherein each bit in the bitmap may correspond to a SCell and the valueof the bit indicates an activation status or deactivation status of theSCell.

An SCell may also be deactivated in response to expiry of a SCelldeactivation timer of the SCell. The expiry of an SCell deactivationtimer of an SCell may be an indication of low activity (e.g., lowtransmission or reception activity) on the SCell. The base station mayconfigure the SCell with an SCell deactivation timer. The base stationmay not configure an SCell deactivation timer for an SCell that isconfigured with PUCCH (also referred to as a PUCCH SCell). Theconfiguration of the SCell deactivation timer may be per configuredSCell and different SCells may be configured with different SCelldeactivation timer values. The SCell deactivation timer may be restartedbased on one or more criteria including reception of downlink controlinformation on the SCell indicating uplink grant or downlink assignmentfor the SCell or reception of downlink control information on ascheduling cell indicating uplink grant or downlink assignment for theSCell or transmission of a MAC PDU based on a configured uplink grant orreception of a configured downlink assignment.

A PCell for a UE may be an SCell for another UE and a SCell for a UE maybe PCell for another UE. The configuration of PCell may be UE-specific.One or more SCells of the multiple SCells configured for a UE may beconfigured as downlink-only SCells, e.g., may only be used for downlinkreception and may not be used for uplink transmission. In case ofself-scheduling, the base station may transmit signaling for uplinkgrants and/or downlink assignments on the same cell that thecorresponding uplink or downlink transmission takes place. In case ofcross-carrier scheduling, the base station may transmit signaling foruplink grants and/or downlink assignments on a cell different from thecell that the corresponding uplink or downlink transmission takes place.

FIG. 11B shows examples of uplink control channel groups in accordancewith several of various embodiments of the present disclosure. A basestation may configure a UE with multiple PUCCH groups wherein a PUCCHgroup comprises one or more cells. For example, as shown in FIG. 11B,the base station may configure a UE with a primary PUCCH group 1114 anda secondary PUCCH group 1116. The primary PUCCH group may comprise thePCell 1110 and one or more first SCells. First UCI corresponding to thePCell and the one or more first SCells of the primary PUCCH group may betransmitted by the PUCCH of the PCell. The first UCI may be, forexample, HARQ feedback for downlink transmissions via downlink CCs ofthe PCell and the one or more first SCells. The secondary PUCCH groupmay comprise a PUCCH SCell and one or more second SCells. Second UCIcorresponding to the PUCCH SCell and the one or more second SCells ofthe secondary PUCCH group may be transmitted by the PUCCH of the PUCCHSCell. The second UCI may be, for example, HARQ feedback for downlinktransmissions via downlink CCs of the PUCCH SCell and the one or moresecond SCells.

FIG. 12A, FIG. 12B and FIG. 12C show example random access processes inaccordance with several of various embodiments of the presentdisclosure. FIG. 12A shows an example of four step contention-basedrandom access (CBRA) procedure. The four-step CBRA procedure includesexchanging four messages between a UE and a base station. Msg1 may befor transmission (or retransmission) of a random access preamble by thewireless device to the base station. Msg2 may be the random accessresponse (RAR) by the base station to the wireless device. Msg3 is thescheduled transmission based on an uplink grant indicated in Msg2 andMsg4 may be for contention resolution.

The base station may transmit one or more RRC messages comprisingconfiguration parameters of the random access parameters. The randomaccess parameters may indicate radio resources (e.g., time-frequencyresources) for transmission of the random access preamble (e.g., Msg1),configuration index, one or more parameters for determining the power ofthe random access preamble (e.g., a power ramping parameter, a preamblereceived target power, etc.), a parameter indicating maximum number ofpreamble transmission, RAR window for monitoring RAR, cell-specificrandom access parameters and UE specific random access parameters. TheUE-specific random access parameters may indicate one or more PRACHoccasions for random access preamble (e.g., Msg1) transmissions. Therandom access parameters may indicate association between the PRACHoccasions and one or more reference signals (e.g., SSB or CSI-RS). Therandom access parameters may further indicate association between therandom access preambles and one or more reference signals (e.g., SBB orCSI-RS). The UE may use one or more reference signals (e.g., SSB(s) orCSI-RS(s)) and may determine a random access preamble to use for Msg1transmission based on the association between the random accesspreambles and the one or more reference signals. The UE may use one ormore reference signals (e.g., SSB(s) or CSI-RS(s)) and may determine thePRACH occasion to use for Msg1 transmission based on the associationbetween the PRACH occasions and the reference signals. The UE mayperform a retransmission of the random access preamble if no response isreceived with the RAR window following the transmission of the preamble.UE may use a higher transmission power for retransmission of thepreamble. UE may determine the higher transmission power of the preamblebased on the power ramping parameter.

Msg2 is for transmission of RAR by the base station. Msg2 may comprise aplurality of RARs corresponding to a plurality of random accesspreambles transmitted by a plurality of UEs. Msg2 may be associated witha random access temporary radio identifier (RA-RNTI) and may be receivedin a common search space of the UE. The RA-RNTI may be based on thePRACH occasion (e.g., time and frequency resources of a PRACH) in whicha random access preamble is transmitted. RAR may comprise a timingadvance command for uplink timing adjustment at the UE, an uplink grantfor transmission of Msg3 and a temporary C-RNTI. In response to thesuccessful reception of Msg2, the UE may transmit the Msg3. Msg3 andMsg4 may enable contention resolution in case of CBRA. In a CBRA, aplurality of UEs may transmit the same random access preamble and mayconsider the same RAR as being corresponding to them. UE may include adevice identifier in Msg3 (e.g., a C-RNTI, temporary C-RNTI or other UEidentity). Base station may transmit the Msg4 with a PDSCH and UE mayassume that the contention resolution is successful in response to thePDSCH used for transmission of Msg4 being associated with the UEidentifier included in Msg3.

FIG. 12B shows an example of a contention-free random access (CFRA)process. Msg 1 (random access preamble) and Msg 2 (random accessresponse) in FIG. 12B for CFRA may be analogous to Msg 1 and Msg 2 inFIG. 12A for CBRA. In an example, the CFRA procedure may be initiated inresponse to a PDCCH order from a base station. The PDCCH order forinitiating the CFRA procedure by the wireless device may be based on aDCI having a first format (e.g., format 1_0). The DCI for the PDCCHorder may comprise a random access preamble index, an UL/SUL indicatorindicating an uplink carrier of a cell (e.g., normal uplink carrier orsupplementary uplink carrier) for transmission of the random accesspreamble, a SS/PBCH index indicating the SS/PBCH that may be used todetermine a RACH occasion for PRACH transmission, a PRACH mask indexindicating the RACH occasion associated with the SS/PBCH indicated bythe SS/PBCH index for PRACH transmission, etc. In an example, the CFRAprocess may be started in response to a beam failure recovery process.The wireless device may start the CFRA for the beam failure recoverywithout a command (e.g., PDCCH order) from the base station and by usingthe wireless device dedicated resources.

FIG. 12C shows an example of a two-step random access process comprisingtwo messages exchanged between a wireless device and a base station. MsgA may be transmitted by the wireless device to the base station and maycomprise one or more transmissions of a preamble and/or one or moretransmissions of a transport block. The transport block in Msg A and Msg3 in FIG. 12A may have similar and/or equivalent contents. The transportblock of Msg A may comprise data and control information (e.g., SR, HARQfeedback, etc.). In response to the transmission of Msg A, the wirelessdevice may receive Msg B from the base station. Msg B in FIG. 12C andMsg 2 (e.g., RAR) illustrated in FIGS. 12A and 12B may have similarand/or equivalent content.

The base station may periodically transmit synchronization signals(SSs), e.g., primary SS (PSS) and secondary SS (SSS) along with PBCH oneach NR cell. The PSS/SSS together with PBCH is jointly referred to as aSS/PBCH block. The SS/PBCH block enables a wireless device to find acell when entering to the mobile communications network or find newcells when moving within the network. The SS/PBCH block spans four OFDMsymbols in time domain. The PSS is transmitted in the first symbol andoccupies 127 subcarriers in frequency domain. The SSS is transmitted inthe third OFDM symbol and occupies the same 127 subcarriers as the PSS.There are eight and nine empty subcarriers on each side of the SSS. ThePBCH is transmitted on the second OFDM symbol occupying 240 subcarriers,the third OFDM symbol occupying 48 subcarriers on each side of the SSS,and on the fourth OFDM symbol occupying 240 subcarriers. Some of thePBCH resources indicated above may be used for transmission of thedemodulation reference signal (DMRS) for coherent demodulation of thePBCH. The SS/PBCH block is transmitted periodically with a periodranging from 5 ms to 160 ms. For initial cell search or for cell searchduring inactive/idle state, a wireless device may assume that that theSS/PBCH block is repeated at least every 20 ms.

In NR, transmissions using of antenna arrays, with many antennaelements, and beamforming plays an important role specially in higherfrequency bands. Beamforming enables higher capacity by increasing thesignal strength (e.g., by focusing the signal energy in a specificdirection) and by lowering the amount interference received at thewireless devices. The beamforming techniques may generally be divided toanalog beamforming and digital beamforming techniques. With digitalbeamforming, signal processing for beamforming is carried out in thedigital domain before digital-to-analog conversion and detailed controlof both amplitude and phase of different antenna elements may bepossible. With analog beamforming, the signal processing for beamformingis carried out in the analog domain and after the digital to analogconversion. The beamformed transmissions may be in one direction at atime. For example, the wireless devices that are in different directionsrelative to the base station may receive their downlink transmissions atdifferent times. For analog receiver-side beamforming, the receiver mayfocus its receiver beam in one direction at a time.

In NR, the base station may use beam sweeping for transmission ofSS/PBCH blocks. The SS/PBCH blocks may be transmitted in different beamsusing time multiplexing. The set of SS/PBCH blocks that are transmittedin one beam sweep may be referred to as a SS/PBCH block set. The periodof PBCH/SSB block transmission may be a time duration between a SS/PBCHblock transmission in a beam and the next SS/PBCH block transmission inthe same beam. The period of SS/PBCH block is, therefore, also theperiod of the SS/PBCH block set.

FIG. 13A shows example time and frequency structure of SS/PBCH blocksand their associations with beams in accordance with several of variousembodiments of the present disclosure. In this example, a SS/PBCH block(also referred to as SSB) set comprise L SSBs wherein an SSB in the SSBset is associated with (e.g., transmitted in) one of L beams of a cell.The transmission of SBBs of an SSB set may be confined within a 5 msinterval, either in a first half-frame or a second half-frame of a 10 msframe. The number of SSBs in an SSB set may depend on the frequency bandof operation. For example, the number of SSBs in a SSB set may be up tofour SSBs in frequency bands below 3 GHz enabling beam sweeping of up tofour beams, up to eight SSBs in frequency bands between 3 GHz and 6 GHzenabling beam sweeping of up to eight beams, and up to sixty four SSBsin higher frequency bands enabling beam sweeping of up to sixty fourbeams. The SSs of an SSB may depend on a physical cell identity (PCI) ofthe cell and may be independent of which beam of the cell is used fortransmission of the SSB. The PBCH of an SSB may indicate a time indexparameter and the wireless device may determine the relative position ofthe SSB within the SSB set using the time index parameter. The wirelessdevice may use the relative position of the SSB within an SSB set fordetermining the frame timing and/or determining RACH occasions for arandom access process.

A wireless device entering the mobile communications network may firstsearch for the PSS. After detecting the PSS, the wireless device maydetermine the synchronization up to the periodicity of the PSS. Bydetecting the PSS, the wireless device may determine the transmissiontiming of the SSS. The wireless device may determine the PCI of the cellafter detecting the SSS. The PBCH of a SS/PBCH block is a downlinkphysical channel that carries the MIB. The MIB may be used by thewireless device to obtain remaining system information (RMSI) that isbroadcast by the network. The RMSI may include System Information Block1 (SIB1) that contains information required for the wireless device toaccess the cell.

As discussed earlier, the wireless device may determine a time indexparameter from the SSB. The PBCH comprises a half-frame parameterindicating whether the SSB is in the first 5 ms half or the second 5 mshalf of a 10 ms frame. The wireless device may determine the frameboundary using the time index parameter and the half-frame parameter. Inaddition, the PBCH may comprise a parameter indicating the system framenumber (SFN) of the cell.

The base station may transmit CSI-RS and a UE may measure the CSI-RS toobtain channel state information (CSI). The base station may configurethe CSI-RS in a UE-specific manner. In some scenarios, same set ofCSI-RS resources may be configured for multiple UEs and one or moreresource elements of a CSI-RS resource may be shared among multiple UEs.A CSI-RS resource may be configured such that it does not collide with aCORESET configured for the wireless device and/or with a DMRS of a PDSCHscheduled for the wireless device and/or transmitted SSBs. The UE maymeasure one or more CSI-RS s configured for the UE and may generate aCSI report based on the CSI-RS measurements and may transmit the CSIreport to the base station for scheduling, link adaptation and/or otherpurposes.

NR supports flexible CSI-RS configurations. A CSI-RS resource may beconfigured with single or multiple antenna ports and with configurabledensity. Based on the number of configured antenna ports, a CSI-RSresource may span different number of OFDM symbols (e.g., 1, 2, and 4symbols). The CSI-RS may be configured for a downlink BWP and may usethe numerology of the downlink BWP. The CSI-RS may be configured tocover the full bandwidth of the downlink BWP or a portion of thedownlink BWP. In some case, the CSI-RS may be repeated in every resourceblock of the CSI-RS bandwidth, referred to as CSI-RS with density equalto one. In some cases, the CSI-RS may be configured to be repeated inevery other resource block of the CSI-RS bandwidth. CSI-RS may benon-zero power (NZP) CSI-RS or zero-power (ZP) CSI-RS.

The base station may configure a wireless device with one or more setsof NZP CSI-RS resources. The base station may configure the wirelessdevice with a NZP CSI-RS resource set using an RRC information element(IE) NZP-CSI-RS-ResourceSet indicating a NZP CSI-RS resource setidentifier (ID) and parameters specific to the NZP CSI-RS resource set.An NZP CSI-RS resource set may comprise one or more CSI-RS resources. AnNZP CSI-RS resource set may be configured as part of the CSI measurementconfiguration.

The CSI-RS may be configured for periodic, semi-persistent or aperiodictransmission. In case of the periodic and semi-persistent CSI-RSconfigurations, the wireless device may be configured with a CSIresource periodicity and offset parameter that indicate a periodicityand corresponding offset in terms of number of slots. The wirelessdevice may determine the slots that the CSI-RS s are transmitted. Forsemi-persistent CSI-RS, the CSI-RS resources for CSI-RS transmissionsmay be activated and deactivated by using a semi-persistent (SP) CSI-CSIResource Set Activation/Deactivation MAC CE. In response to receiving aMAC CE indicating activation of semi-persistent CSI-RS resources, thewireless device may assume that the CSI-RS transmissions will continueuntil the CSI-RS resources for CSI-RS transmissions are activated.

As discussed before, CSI-RS may be configured for a wireless device asNZP CSI-RS or ZP CSI-RS. The configuration of the ZP CSI-RS may besimilar to the NZP CSI-RS with the difference that the wireless devicemay not carry out measurements for the ZP CSI-RS. By configuring ZPCSI-RS, the wireless device may assume that a scheduled PDSCH thatincludes resource elements from the ZP CSI-RS is rate matched aroundthose ZP CSI-RS resources. For example, a ZP CSI-RS resource configuredfor a wireless device may be an NZP CSI-RS resource for another wirelessdevice. For example, by configuring ZP CSI-RS resources for the wirelessdevice, the base station may indicate to the wireless device that thePDSCH scheduled for the wireless device is rate matched around the ZPCSI-RS resources.

A base station may configure a wireless device with channel stateinformation interference measurement (CSI-IM) resources. Similar to theCSI-RS configuration, configuration of locations and density of CSI-IMresources may be flexible. The CSI-IM resources may be periodic(configured with a periodicity), semi-persistent (configured with aperiodicity and activated and deactivated by MAC CE) or aperiodic(triggered by a DCI).

Tracking reference signals (TRSs) may be configured for a wirelessdevice as a set of sparse reference signals to assist the wireless intime and frequency tracking and compensating time and frequencyvariations in its local oscillator. The wireless device may further usethe TRSs for estimating channel characteristics such as delay spread ordoppler frequency. The base station may use a CSI-RS configuration forconfiguring TRS for the wireless device. The TRS may be configured as aresource set comprising multiple periodic NZP CSI-RS resources.

A base station may configure a UE and the UE may transmit soundingreference signals (SRSs) to enable uplink channel sounding/estimation atthe base station. The SRS may support up to four antenna ports and maybe designed with low cubic metric enabling efficient operation of thewireless device amplifier. The SRS may span one or more (e.g., one, twoor four) consecutive OFDM symbols in time domain and may be locatedwithin the last n (e.g., six) symbols of a slot. In the frequencydomain, the SRS may have a structure that is referred to as a combstructure and may be transmitted on every Nth subcarrier. Different SRStransmissions from different wireless devices may have different combstructures and may be multiplexed in frequency domain.

A base station may configure a wireless device with one or more SRSresource sets and an SRS resource set may comprise one or more SRSresources. The SRS resources in an SRS resources set may be configuredfor periodic, semi-persistent or aperiodic transmission. The periodicSRS and the semi-persistent SRS resources may be configured withperiodicity and offset parameters. The Semi-persistent SRS resources ofa configured semi-persistent SRS resource set may be activated ordeactivated by a semi-persistent (SP) SRS Activation/Deactivation MACCE. The set of SRS resources included in an aperiodic SRS resource setmay be activated by a DCI. A value of a field (e.g., an SRS requestfield) in the DCI may indicate activation of resources in an aperiodicSRS resource set from a plurality of SRS resource sets configured forthe wireless device.

An antenna port may be associated with one or more reference signals.The receiver may assume that the one or more reference signals,associated with the antenna port, may be used for estimating channelcorresponding to the antenna port. The reference signals may be used toderive channel state information related to the antenna port. Twoantenna ports may be referred to as quasi co-located if characteristics(e.g., large-scale properties) of the channel over which a symbol isconveyed on one antenna port may be inferred from the channel over whicha symbol is conveyed from another antenna port. For example, a UE mayassume that radio channels corresponding to two different antenna portshave the same large-scale properties if the antenna ports are specifiedas quasi co-located. In some cases, the UE may assume that two antennaports are quasi co-located based on signaling received from the basestation. Spatial quasi-colocation (QCL) between two signals may be, forexample, due to the two signals being transmitted from the same locationand in the same beam. If a receive beam is good for a signal in a groupof signals that are spatially quasi co-located, it may be assumed alsobe good for the other signals in the group of signals.

The CSI-RS in the downlink and the SRS in uplink may serve asquasi-location (QCL) reference for other physical downlink channels andphysical uplink channels, respectively. For example, a downlink physicalchannel (e.g., PDSCH or PDCCH) may be spatially quasi co-located with adownlink reference signal (e.g., CSI-RS or SSB). The wireless device maydetermine a receive beam based on measurement on the downlink referencesignal and may assume that the determined received beam is also good forreception of the physical channels (e.g., PDSCH or PDCCH) that arespatially quasi co-located with the downlink reference signal.Similarly, an uplink physical channel (e.g., PUSCH or PUCCH) may bespatially quasi co-located with an uplink reference signal (e.g., SRS).The base station may determine a receive beam based on measurement onthe uplink reference signal and may assume that the determined receivedbeam is also good for reception of the physical channels (e.g., PUSCH orPUCCH) that are spatially quasi co-located with the uplink referencesignal.

The Demodulation Reference Signals (DM-RS s) enables channel estimationfor coherent demodulation of downlink physical channels (e.g., PDSCH,PDCCH and PBH) and uplink physical channels (e.g., PUSCH and PUCCH). TheDM-RS may be located early in the transmission (e.g., front-loadedDM-RS) and may enable the receiver to obtain the channel estimate earlyand reduce the latency. The time-domain structure of the DM-RS (e.g.,symbols wherein the DM-RS are located in a slot) may be based ondifferent mapping types.

The Phase Tracking Reference Signals (PT-RS s) enables tracking andcompensation of phase variations across the transmission duration. Thephase variations may be, for example, due to oscillator phase noise. Theoscillator phase noise may become more sever in higher frequencies(e.g., mmWave frequency bands). The base station may configure the PT-RSfor uplink and/or downlink. The PT-RS configuration parameters mayindicate frequency and time density of PT-RS, maximum number of ports(e.g., uplink ports), resource element offset, configuration of uplinkPT-RS without transform precoder (e.g., CP-OFDM) or with transformprecoder (e.g., DFT-s-OFDM), etc. The subcarrier number and/or resourceblocks used for PT-RS transmission may be based on the C-RNTI of thewireless device to reduce risk of collisions between PT-RS s of wirelessdevices scheduled on overlapping frequency domain resources.

FIG. 13B shows example time and frequency structure of CSI-RS s andtheir association with beams in accordance with several of variousembodiments of the present disclosure. A beam of the L beams shown inFIG. 13B may be associated with a corresponding CSI-RS resource. Thebase station may transmit the CSI-RS s using the configured CSI-RSresources and a UE may measure the CSI-RS s (e.g., received signalreceived power (RSRP) of the CSI-RS s) and report the CSI-RSmeasurements to the base station based on a reporting configuration. Forexample, the base station may determine one or more transmissionconfiguration indication (TCI) states and may indicate the one or moreTCI states to the UE (e.g., using RRC signaling, a MAC CE and/or a DCI).Based on the one or more TCI states indicated to the UE, the UE maydetermine a downlink receive beam and receive downlink transmissionsusing the receive beam. In case of a beam correspondence, the UE maydetermine a spatial domain filter of a transmit beam based on spatialdomain filter of a corresponding receive beam. Otherwise, the UE mayperform an uplink beam selection procedure to determine the spatialdomain filter of the transmit beam. The UE may transmit one or more SRSsusing the SRS resources configured for the UE and the base station maymeasure the SRSs and determine/select the transmit beam for the UE basedthe SRS measurements. The base station may indicate the selected beam tothe UE. The CSI-RS resources shown in FIG. 13B may be for one UE. Thebase station may configure different CSI-RS resources associated with agiven beam for different UEs by using frequency division multiplexing.

A base station and a wireless device may perform beam managementprocedures to establish beam pairs (e.g., transmit and receive beams)that jointly provide good connectivity. For example, in the downlinkdirection, the UE may perform measurements for a beam pair and estimatechannel quality for a transmit beam by the base station (or atransmission reception point (TRP) more generally) and the receive beamby the UE. The UE may transmit a report indicating beam pair qualityparameters. The report may comprise one or more parameters indicatingone or more beams (e.g., a beam index, an identifier of reference signalassociated with a beam, etc.), one or more measurement parameters (e.g.,RSRP), a precoding matrix indicator (PMI), a channel quality indicator(CQI), and/or a rank indicator (RI).

FIG. 14A, FIG. 14B and FIG. 14C show example beam management processes(referred to as P1, P2 and P3, respectively) in accordance with severalof various embodiments of the present disclosure. The P1 process shownin FIG. 14A may enable, based on UE measurements, selection of a basestation (or TRP more generally) transmit beam and/or a wireless devicereceive beam. The TRP may perform a beam sweeping procedure where theTRP may sequentially transmit reference signals (e.g., SSB and/orCSI-RS) on a set of beams and the UE may select a beam from the set ofbeams and may report the selected beam to the TRP. The P2 procedure asshown in FIG. 14B may be a beam refinement procedure. The selection ofthe TRP transmit beam and the UE receive beam may be regularlyreevaluated due to movements and/or rotations of the UE or movement ofother objects. In an example, the base station may perform the beamsweeping procedure over a smaller set of beams and the UE may select thebest beam over the smaller set. In an example, the beam shape may benarrower compared to beam selected based on the P1 procedure. Using theP3 procedure as shown in FIG. 14C, the TRP may fix its transmit beam andthe UE may refine its receive beam.

A wireless device may receive one or more messages from a base station.The one or more messages may comprise one or more RRC messages. The oneor more messages may comprise configuration parameters of a plurality ofcells for the wireless device. The plurality of cells may comprise aprimary cell and one or more secondary cells. For example, the pluralityof cells may be provided by a base station and the wireless device maycommunicate with the base station using the plurality of cells. Forexample, the plurality of cells may be provided by multiple base station(e.g., in case of dual and/or multi-connectivity). The wireless devicemay communicate with a first base station, of the multiple basestations, using one or more first cells of the plurality of cells. Thewireless device may communicate with a second base station of themultiple base stations using one or more second cells of the pluralityof cells.

The one or more messages may comprise configuration parameters used forprocesses in physical, MAC, RLC, PCDP, SDAP, and/or RRC layers of thewireless device. For example, the configuration parameters may includevalues of timers used in physical, MAC, RLC, PCDP, SDAP, and/or RRClayers. For example, the configuration parameters may include parametersfor configurating different channels (e.g., physical layer channel,logical channels, RLC channels, etc.) and/or signals (e.g., CSI-RS, SRS,etc.).

Upon starting a timer, the timer may start running until the timer isstopped or until the timer expires. A timer may be restarted if it isrunning. A timer may be started if it is not running (e.g., after thetimer is stopped or after the timer expires). A timer may be configuredwith or may be associated with a value (e.g., an initial value). Thetimer may be started or restarted with the value of the timer. The valueof the timer may indicate a time duration that the timer may be runningupon being started or restarted and until the timer expires. Theduration of a timer may not be updated until the timer is stopped orexpires (e.g., due to BWP switching). This specification may disclose aprocess that includes one or more timers. The one or more timers may beimplemented in multiple ways. For example, a timer may be used by thewireless device and/or base station to determine a time window [t1, t2],wherein the timer is started at time t1 and expires at time t2 and thewireless device and/or the base station may be interested in and/ormonitor the time window [t1, t2], for example to receive a specificsignaling. Other examples of implementation of a timer may be provided.

FIG. 15 shows example components of a wireless device and a base stationthat are in communication via an air interface in accordance withseveral of various embodiments of the present disclosure. The wirelessdevice 1502 may communicate with the base station 1542 over the airinterface 1532. The wireless device 1502 may include a plurality ofantennas. The base station 1542 may include a plurality of antennas. Theplurality of antennas at the wireless device 1502 and/or the basestation 1542 enables different types of multiple antenna techniques suchas beamforming, single-user and/or multi-user MIMO, etc.

The wireless device 1502 and the base station 1542 may have one or moreof a plurality of modules/blocks, for example RF front end (e.g., RFfront end 1530 at the wireless device 1502 and RF front end 1570 at thebase station 1542), Data Processing System (e.g., Data Processing System1524 at the wireless device 1502 and Data Processing System 1564 at thebase station 1542), Memory (e.g., Memory 1512 at the wireless device1502 and Memory 1542 at the base station 1542). Additionally, thewireless device 1502 and the base station 1542 may have othermodules/blocks such as GPS (e.g., GPS 1514 at the wireless device 1502and GPS 1554 at the base station 1542).

An RF front end module/block may include circuitry between antennas anda Data Processing System for proper conversion of signals between thesetwo modules/blocks. An RF front end may include one or more filters(e.g., Filter(s) 1526 at RF front end 1530 or Filter(s) 1566 at the RFfront end 1570), one or more amplifiers (e.g., Amplifier(s) 1528 at theRF front end 1530 and Amplifier(s) 1568 at the RF front end 1570). TheAmplifier(s) may comprise power amplifier(s) for transmission andlow-noise amplifier(s) (LNA(s)) for reception.

The Data Processing System 1524 and the Data Processing System 1564 mayprocess the data to be transmitted or the received signals byimplementing functions at different layers of the protocol stack such asPHY, MAC, RLC, etc. Example PHY layer functions that may be implementedby the Data Processing System 1524 and/or 1564 may include forward errorcorrection, interleaving, rate matching, modulation, precoding, resourcemapping, MIMO processing, etc. Similarly, one or more functions of theMAC layer, RLC layer and/or other layers may be implemented by the DataProcessing System 1524 and/or the Data Processing System 1564. One ormore processes described in the present disclosure may be implemented bythe Data Processing System 1524 and/or the Data Processing System 1564.A Data Processing System may include an RF module (RF module 1516 at theData Processing System 1524 and RF module 1556 at the Data ProcessingSystem 1564) and/or a TX/RX processor (e.g., TX/RX processor 1518 at theData Processing System 1524 and TX/RX processor 1558 at the DataProcessing System 1566) and/or a central processing unit (CPU) (e.g.,CPU 1520 at the Data Processing System 1524 and CPU 1560 at the DataProcessing System 1564) and/or a graphical processing unit (GPU) (e.g.,GPU 1522 at the Data Processing System 1524 and GPU 1562 at the DataProcessing System 1564).

The Memory 1512 may have interfaces with the Data Processing System 1524and the Memory 1552 may have interfaces with Data Processing System1564, respectively. The Memory 1512 or the Memory 1552 may includenon-transitory computer readable mediums (e.g., Storage Medium 1510 atthe Memory 1512 and Storage Medium 1550 at the Memory 1552) that maystore software code or instructions that may be executed by the DataProcessing System 1524 and Data Processing System 1564, respectively, toimplement the processes described in the present disclosure. The Memory1512 or the Memory 1552 may include random-access memory (RAM) (e.g.,RAM 1506 at the Memory 1512 or RAM 1546 at the Memory 1552) or read-onlymemory (ROM) (e.g., ROM 1508 at the Memory 1512 or ROM 1548 at theMemory 1552) to store data and/or software codes.

The Data Processing System 1524 and/or the Data Processing System 1564may be connected to other components such as a GPS module 1514 and a GPSmodule 1554, respectively, wherein the GPS module 1514 and a GPS module1554 may enable delivery of location information of the wireless device1502 to the Data Processing System 1524 and location information of thebase station 1542 to the Data Processing System 1564. One or more otherperipheral components (e.g., Peripheral Component(s) 1504 or PeripheralComponent(s) 1544) may be configured and connected to the dataProcessing System 1524 and data Processing System 1564, respectively.

In example embodiments, a wireless device may be configured withparameters and/or configuration arrangements. For example, theconfiguration of the wireless device with parameters and/orconfiguration arrangements may be based on one or more control messagesthat may be used to configure the wireless device to implement processesand/or actions. The wireless device may be configured with theparameters and/or the configuration arrangements regardless of thewireless device being in operation or not in operation. For example,software, firmware, memory, hardware and/or a combination thereof and/oralike may be configured in a wireless device regardless of the wirelessdevice being in operation or not operation. The configured parametersand/or settings may influence the actions and/or processes performed bythe wireless device when in operation.

In example embodiments, a wireless device may receive one or moremessage comprising configuration parameters. For example, the one ormore messages may comprise radio resource control (RRC) messages. Aparameter of the configuration parameters may be in at least one of theone or more messages. The one or more messages may comprise informationelement (IEs). An information element may be a structural element thatincludes single or multiple fields. The fields in an IE may beindividual contents of the IE. The terms configuration parameter, IE andfield may be used equally in this disclosure. The IEs may be implementedusing a nested structure, wherein an IE may include one or more otherIEs and an IE of the one or more other IEs may include one or moreadditional IEs. With this structure, a parent IE contains all theoffspring IEs as well. For example, a first IE containing a second IE,the second IE containing a third IE, and the third IE containing afourth IE may imply that the first IE contains the third IE and thefourth IE.

Example embodiments may enable mechanism and procedures of L1/L2 basedinter-cell mobility, for example for mobility latency reduction. Inexample embodiments, multiple candidate cells may beconfigured/pre-configured and the configurations of the multiplecandidate cells may be maintained to allow fast application ofconfigurations for candidate cells in response to L1/L2 signaling. Inexample embodiments, dynamic switch/mobility (e.g., mobility, e.g.,inter-cell mobility) mechanisms among candidate serving cells (includingSpCell and SCell) based on L1/L2 signaling may be enabled.

In an example, L1/L2 based mobility (e.g., inter-cell mobility) mayreduce the user plane data interruption compared with L3 controlledmobility solutions. In an example L1/L2 based mobility solution,candidate cells may be configured/pre-configured. A wireless device maystore the configuration and may perform measurement and beam managementand the UE may initiate fast cell switching based on L1/L2 signaling.

In an example, network-controlled mobility may apply to UEs inRRC_CONNECTED and may be categorized into two types of mobility: celllevel mobility and beam level mobility.

In an example, cell level mobility may require explicit RRC signaling tobe triggered (e.g., handover). For inter-gNB handover, the signalingprocedures may comprise at least the following elemental componentsillustrated in FIG. 16 : the source gNB may initiate handover and mayissue a HANDOVER REQUEST over the Xn interface. The target gNB mayperform admission control and may provide the new RRC configuration aspart of the HANDOVER REQUEST ACKNOWLEDGE. The source gNB may provide theRRC configuration to the UE by forwarding the RRCReconfiguration messagereceived in the HANDOVER REQUEST ACKNOWLEDGE. The RRCReconfigurationmessage may include at least cell ID and information required to accessthe target cell so that the UE may access the target cell withoutreading system information. For some cases, the information required forcontention-based and contention-free random access may be included inthe RRCReconfiguration message. The access information to the targetcell may include beam specific information, if any. The UE may move theRRC connection to the target gNB and may reply with theRRCReconfigurationComplete.

In an example, in case of DAPS handover, the UE may continue thedownlink user data reception from the source gNB until releasing thesource cell and may continue the uplink user data transmission to thesource gNB until successful random access procedure to the target gNB.

In an example, beam level mobility may not require explicit RRCsignaling to be triggered. The gNB may provide, via RRC signaling, theUE with measurement configuration containing configurations of SSB/CSIresources and resource sets, reports and trigger states for triggeringchannel and interference measurements and reports. Beam level mobilitymay be dealt with at lower layers by means of physical layer and MAClayer control signaling, and RRC may not be required to know which beamis being used at a given point in time.

In an example, SSB-based beam level mobility may be based on the SSBassociated to the initial DL BWP and may be configured for the initialDL BWPs and for DL BWPs containing the SSB associated to the initial DLBWP. For other DL BWPs, beam level mobility may be performed based onCSI-RS.

In an example, in RRC_CONNECTED, a wireless device may measure one ormore beams (e.g., at least one beam) of a cell and the measurementsresults (e.g., power values) may be averaged to derive the cell quality.In doing so, the UE may be configured to consider a subset of thedetected beams. Filtering may take place at two different levels: at thephysical layer to derive beam quality and then at RRC level to derivecell quality from multiple beams. Cell quality from beam measurementsmay be derived in the same way for the serving cell(s) and for thenon-serving cell(s). Measurement reports may contain the measurementresults of the X best beams if the UE is configured to do so by the gNB.

In an example, measurement reports may characterized by the following:measurement reports may include the measurement identity of theassociated measurement configuration that triggered the reporting; celland beam measurement quantities to be included in measurement reportsmay be configured by the network; the number of non-serving cells to bereported may be limited through configuration by the network; cellsbelonging to a blacklist configured by the network may not be used inevent evaluation and reporting, and conversely when a whitelist isconfigured by the network, the cells belonging to the whitelist may beused in event evaluation and reporting; beam measurements to be includedin measurement reports may be configured by the network (e.g., beamidentifier only, measurement result and beam identifier, or no beamreporting).

In an example, intra-frequency neighbor (cell) measurements andinter-frequency neighbor (cell) measurements may be defined as follows.SSB based intra-frequency measurement: a measurement is defined as anSSB based intra-frequency measurement provided the center frequency ofthe SSB of the serving cell and the center frequency of the SSB of theneighbor cell are the same, and the subcarrier spacing of the two SSBsis also the same; SSB based inter-frequency measurement: a measurementmay be defined as an SSB based inter-frequency measurement provided thecenter frequency of the SSB of the serving cell and the center frequencyof the SSB of the neighbor cell may be different, or the subcarrierspacing of the two SSBs may be different. CSI-RS based intra-frequencymeasurement: a measurement is defined as a CSI-RS based intra-frequencymeasurement.

In an example, a closed loop Demodulation Reference Signal (DMRS) basedspatial multiplexing may be supported for Physical Downlink SharedChannel (PDSCH).

In an example, the DMRS and corresponding PDSCH may be transmitted usingthe same precoding matrix and the UE may not need to know the precodingmatrix to demodulate the transmission. The transmitter may use differentprecoder matrix for different parts of the transmission bandwidth,resulting in frequency selective precoding. The UE may assume that thesame precoding matrix is used across a set of Physical Resource Blocks(PRBs) denoted Precoding Resource Block Group (PRG).

In an example, the UE may assume that at least one symbol withdemodulation reference signal is present on each layer in which PDSCH istransmitted to a UE, and up to 3 additional DMRS may be configured byhigher layers.

In an example, a closed loop DMRS based spatial multiplexing may besupported for PUSCH. For a given UE, up to 4 layer transmissions may besupported.

In an example, the UE may transmit at least one symbol with demodulationreference signal on each layer on each frequency hop in which the PUSCHis transmitted, and up to 3 additional DMRS may be configured by higherlayers.

In an example, a MAC PDU may be a bit string that may be byte aligned(e.g., multiple of 8 bits) in length. In an example, bit strings may berepresented by tables in which the most significant bit is the leftmostbit of the first line of the table, the least significant bit is therightmost bit on the last line of the table, and more generally the bitstring is to be read from left to right and then in the reading order ofthe lines. The bit order of each parameter field within a MAC PDU may berepresented with the first and most significant bit in the leftmost bitand the last and least significant bit in the rightmost bit. A MAC SDUmay be a bit string that may be byte aligned (e.g., multiple of 8 bits)in length. A MAC SDU may be included into a MAC PDU from the first bitonward. In an example, a MAC CE may be a bit string that is byte aligned(e.g., multiple of 8 bits) in length. A MAC subheader may be a bitstring that may be byte aligned (e.g., multiple of 8 bits) in length.Each MAC subheader may be placed immediately in front of thecorresponding MAC SDU, MAC CE, or padding.

In an example, a MAC PDU may consist of one or more MAC subPDUs. EachMAC subPDU may comprise one of the following: a MAC subheader only(including padding); a MAC subheader and a MAC SDU; a MAC subheader anda MAC CE; a MAC subheader and padding.

In an example, RRC may configure the following parameters for themaintenance of UL time alignment: timeAlignmentTimer (per TAG) which maycontrol how long the MAC entity considers the Serving Cells belonging tothe associated TAG to be uplink time aligned.

In an example, when a Timing Advance Command MAC CE is received, and ifan NTA has been maintained with the indicated TAG: the MAC entity mayapply the Timing Advance Command for the indicated TAG; start or restartthe timeAlignmentTimer associated with the indicated TAG.

In an example, when a Timing Advance Command is received in a RandomAccess Response message for a Serving Cell belonging to a TAG or in aMSGB for an SpCell: if the Random Access Preamble was not selected bythe MAC entity among the contention-based Random Access Preamble: theMAC entity may apply the Timing Advance Command for this TAG; start orrestart the timeAlignmentTimer associated with this TAG. If thetimeAlignmentTimer associated with this TAG is not running: the MACentity may apply the Timing Advance Command for this TAG; start thetimeAlignmentTimer associated with this TAG; when the ContentionResolution is considered not successful or when the ContentionResolution is considered successful for SI request, after transmittingHARQ feedback for MAC PDU including UE Contention Resolution IdentityMAC CE: the MAC entity stop timeAlignmentTimer associated with this TAG.

In an example, when an Absolute Timing Advance Command is received inresponse to a MSGA transmission including C-RNTI MAC CE, the MAC entitymay apply the Timing Advance Command for PTAG; start or restart thetimeAlignmentTimer associated with PTAG.

In an example, when a timeAlignmentTimer expires: if thetimeAlignmentTimer is associated with the PTAG: the MAC entity may flushall HARQ buffers for all Serving Cells; notify RRC to release PUCCH forall Serving Cells, if configured; notify RRC to release SRS for allServing Cells, if configured; clear any configured downlink assignmentsand configured uplink grants; clear any PUSCH resource forsemi-persistent CSI reporting; consider all running timeAlignmentTimersas expired; maintain NTA of all TAGs.

In an example, when a timeAlignmentTimer expires: if thetimeAlignmentTimer is associated with an STAG, then for all ServingCells belonging to this TAG: the MAC entity may flush all HARQ buffers;notify RRC to release PUCCH, if configured; notify RRC to release SRS,if configured; clear any configured downlink assignments and configureduplink grants; clear any PUSCH resource for semi-persistent CSIreporting; maintain NTA of this TAG.

In an example, when the MAC entity stops uplink transmissions for anSCell due to the fact that the maximum uplink transmission timingdifference between TAGs of the MAC entity or the maximum uplinktransmission timing difference between TAGs of any MAC entity of the UEis exceeded, the MAC entity may consider the timeAlignmentTimerassociated with the SCell as expired.

In an example, the MAC entity may not perform any uplink transmission ona Serving Cell except the Random Access Preamble and MSGA transmissionwhen the timeAlignmentTimer associated with the TAG to which thisServing Cell belongs is not running. Furthermore, when thetimeAlignmentTimer associated with the PTAG is not running, the MACentity may not perform any uplink transmission on any Serving Cellexcept the Random Access Preamble and MSGA transmission on the SpCell.

In an example, the Timing Advance Command MAC CE may be identified byMAC subheader with an associated LCID. In an example, it may have afixed size as shown in FIG. 17 . In an example, a TAG Identity (TAG ID)field may indicate the TAG Identity of the addressed TAG. The TAGcontaining the SpCell may have the TAG Identity 0. The length of thefield may be 2 bits. A Timing Advance Command field may indicate theindex value TA (e.g., 0, 1, 2 . . . 63) used to control the amount oftiming adjustment that MAC entity may have to apply.

In an example, a UE may compile and transfers its UE capabilityinformation upon receiving a UECapabilityEnquiry from the network.

In an example, the network may initiate a capability transfer procedureto a UE in RRC_CONNECTED when it needs (additional) UE radio accesscapability information. The network may retrieve UE capabilities afterAS security activation.

In an example, the UE may set the contents of UECapabilityInformationmessage.

In an example, if the ue-CapabilityRAT-RequestList contains aUE-CapabilityRAT-Request with rat-Type set to nr: the UE may include inthe ue-CapabilityRAT-ContainerList a UE-CapabilityRAT-Container of thetype UE-NR-Capability and with the rat-Type set to nr; may include thesupportedBandCombinationList, featureSets and featureSetCombinations.

In an example, if the ue-CapabilityRAT-RequestList contains aUE-CapabilityRAT-Request with rat-Type set to eutra-nr: if the UEsupports (NG)EN-DC or NE-DC: the UE may include in theue-CapabilityRAT-ContainerList a UE-CapabilityRAT-Container of the typeUE-MRDC-Capability and with the rat-Type set to eutra-nr; the UE mayinclude the supportedBandCombinationList and featureSetCombinations.

In an example, if the ue-CapabilityRAT-RequestList contains aUE-CapabilityRAT-Request with rat-Type set to eutra: if the UE supportsE-UTRA: the UE may include in the ue-CapabilityRAT-ContainerList aue-CapabilityRAT-Container of the type UE-EUTRA-Capability and with therat-Type set to eutra, according to the capabilityRequestFilter, ifreceived.

In an example, if the ue-CapabilityRAT-RequestList contains aUE-CapabilityRAT-Request with rat-Type set to utra-fdd: if the UEsupports UTRA-FDD: the UE may include the UE radio access capabilitiesfor UTRA-FDD within a ue-CapabilityRAT-Container and with the rat-Typeset to utra-fdd.

In an example, if the RRC message segmentation is enabled based on thefield rrc-SegAllowed received, and the encoded RRC message is largerthan the maximum supported size of a PDCP SDU: the UE may initiate theUL message segment transfer procedure; otherwise the UE may submit theUECapabilityInformation message to lower layers for transmission, uponwhich the procedure may end.

In an example, the UECapabilityEnquiry message may be used to request UEradio access capabilities for NR as well as for other RATs. In anexample, the IE UECapabilityInformation message may be used to transferUE radio access capabilities requested by the network.

When the UE moves from the coverage area of one cell to another cell, atsome point a serving cell change may need to be performed. Existingtriggering mechanisms for serving cell change and/or handover/inter-cellmobility may be based on layer 3 (L3) measurements and may be done byRRC signaling triggered reconfiguration with Synchronization for changeof PCell and PSCell, as well as release add for SCells when applicable.Existing mechanisms for handover or cell/cell group change/switching maylead to a high latency may involve L2 and/or L1 resets leading to longerlatency, larger overhead and longer interruption time than beam switchmobility. There is a need to enhance the existing handover or cell/cellgroup change/switching mechanisms. Example embodiments enhance theexisting handover or cell/cell group change/switching mechanisms.

In example embodiments, a wireless device may receive one or moremessages (e.g., one or more RRC messages) comprising configurationparameters. The configuration parameters may comprise firstconfiguration parameters of one or more first cells, secondconfiguration parameters of one or more second cells, and thirdconfiguration parameters for measurements (e.g., radio resourcemanagement (RRM) measurements to be used for mobility (e.g., handover,e.g., inter-cell handover), cell/cell group switching, etc.)). Thewireless device may receive the one or more messages from a first basestation (BS). The one or more first cells may be associatedwith/of/provided by the first BS. In an example, the one or more secondcells may be associated with/of/provided by the first BS. In an example,the one or more second cells may be provided by a second BS.

In example embodiments, the handover or cell/cell group switching maycomprise changing from one or more first cells to one or more secondcells. For example, in case of handover, the wireless device may changefrom one or more first cells of a first BS to one or more second cellsof a second BS. For example, the changing from the one or more firstcells to the one or more second cells may comprise changing SpCell(e.g., PCell or PSCell), changing a cell group (e.g., secondary cellgroup (SCG) change), changing secondary cell (SCell), etc.

In example embodiments, the third configuration parameters may comprisesignals configuration parameters (e.g., reference signal configurationparameters) of signals (e.g., reference signals) associatedwith/transmitted via the one or more second cells. The wireless devicemay perform measurements for the one or more second cells and/or for thebeams associated with the one or more second cells based on the thirdconfiguration parameters (e.g., based on measuring the signals/referencesignals associated with/transmitted via the one or more second cellsand/or measuring the signals/reference signals corresponding to thebeams associated with the one or more second cells).

In an example embodiment as shown in FIG. 18 , physical layer signaling(e.g., control information transmitted using control channel or physicallayer signal(s)) and/or MAC layer signaling (e.g., MAC CE(s)) may beused to indicate handover from the one or more first cells to the one ormore second cells or may be used to indicate switching from the one ormore first cells to the one or more second cells (e.g., a cell groupchange/switch, a change/switch of SpCell (e.g., PCell/PSCell) a changeof SCell, etc.). In an example, the physical layer signaling and/or theMAC layer signaling may be transmitted/received based on/in response tothe measurement results of the measurements performed using the thirdconfiguration parameters. In response to the physical layer and/or theMAC layer signaling, the wireless device may initiate handover from theone or more first cells to the one or more second cells or may initiateswitching from the one or more first cells to the one or more secondcells.

In example embodiments as shown in FIG. 19 , FIG. 20 and FIG. 21 , thewireless device may transmit a first indication of handover/switchingfrom the one or more first cells to the one or more second cells. In anexample, the wireless device may make a determination ofhandover/switching from the one or more first cells to the one or moresecond cells and may transmit the first indication that the wirelessdevice has made the determination. In an example, the wireless devicemay make a selectin of the one or more second cells forhandover/switching from the one or more first cells to the one or moresecond cells and may transmit the first indication that the wirelessdevice has made the selection.

In an example, the first indication may be via physical layer signalingor may be via MAC layer signaling.

In an example, in case the first indication is via physical layersignaling, the physical layer signaling may be via uplink controlinformation (e.g., UCI to be transmitted via an uplink control channelor to be multiplexed via PUSCH) or via an uplink signal (e.g., via anuplink reference signal such as SRS, DMRS, etc.). In an example, thefirst indication may be via a scheduling request (SR) associated with afirst SR configuration. In an example a sequence associated with theuplink signal (e.g., a sequence (e.g., a sequence number) associatedwith uplink signal, e.g., SRS or DMRS) may be used for the firstindication. The wireless device may receive configuration parameters fortransmission of (e.g., for determining radio resources for transmissionof) the first indication via the uplink control channel (e.g., fortransmission of the UCI or configuration parameters of the first SRconfiguration associated with the first indication) or based on theuplink signal. In case the first indication is based multiplexing UCIvia PUSCH, the wireless device may receive an uplink grant indicatingradio resources for transmission of a transport block via PUSCH andtransmission of the UCI may be via first radio resources of the radioresources indicated by the uplink grant.

In an example, in case the first indication is MAC layer signaling, theMAC layer signaling for transmission of the first indication may be viaa first MAC CE (e.g., an uplink MAC CE). In an example, the first MAC CEmay have a first format associated with L1/L2 based handover/switching.In an example, the first MAC CE may be associated with a first LCID thatis associated with the L1/L2 based handover/switching. The first MAC CEmay be multiplexed in a transport block and the wireless device maytransmit the transport block based on/via an uplink shared/data channel.

In an example, the one or more first cells may be associatedwith/of/provided by the first BS and the one or more second cells may beassociated with/of/provided by the second BS. The first indication,transmitted by the wireless device, may indicate the handover from theone or more first cells of the first BS to the one or more second cellsof the second BS. In response to transmitting the first indication, thewireless device may initiate the handover from the one or more firstcells of the first BS to the one or more second cells of the second BS.In an example, the wireless device may initiate the handover based onsecond configuration parameters of the one or more second cells (e.g.,received prior to the indication).

In an example embodiment as shown in FIG. 20 , the wireless device mayreceive a first acknowledgement in response to transmission of the firstindication indicating successful reception (e.g., by the first BS) ofthe first indication. The wireless device may initiate the handover fromthe one or more first cells of the first BS to the one or more secondcells of the second BS in response to reception of the firstacknowledgement. For example, the wireless device may initiate thehandover on/after an offset from a first timing of reception of thefirst acknowledgement. In an example, the offset may be in a number ofsymbols or in a number of slots. In an example, the offset may bepre-configured. In an example, the offset may be configurable, and thewireless device may receive a configuration parameter indicating theoffset.

In an example, the first acknowledgement may be a HARQ acknowledgement.For example, in case the first indication is via a MAC CE multiplexed ina transport block, the first acknowledgement may indicate successfulreception of the transport block (e.g., by the first BS). The wirelessdevice may initiate the handover from the one or more first cells of thefirst BS to the one or more second cells of the second BS in response toreception of the first HARQ acknowledgement. For example, the wirelessdevice may initiate the handover on/after an offset from a first timingof reception of the first HARQ acknowledgement. In an example, theoffset may be in a number of symbols or in a number of slots. In anexample, the offset may be pre-configured. In an example, the offset maybe configurable, and the wireless device may receive a configurationparameter indicating the offset.

In an example, the first acknowledgement may be via a second MAC CE. Forexample, the second MAC CE may have a zero payload and an LCIDassociated with the second MAC CE may indicate that the second MAC CE isfor an acknowledgement of the first indication. The wireless device mayinitiate the handover from the one or more first cells of the first BSto the one or more second cells of the second BS in response toreception of the second MAC CE. For example, the wireless device mayinitiate the handover on/after an offset from a first timing ofreception of the second MAC CE. In an example, the offset may be in anumber of symbols or in a number of slots. In an example, the offset maybe pre-configured. In an example, the offset may be configurable, andthe wireless device may receive a configuration parameter indicating theoffset.

In an example, the initiating the handover from the one or more firstcells of the first BS to the one or more second cells of the second BSmay comprise initiating one or more random access processes comprisingtransmitting one or more random access preambles via the one or moresecond cells. The initiating the one or more random access processes maybe based on second configurations parameters of the one or more secondcells (e.g., random access configuration parameters indicating randomaccess occasions/parameters).

In an example, in response to transmission of the first indication, thewireless device may communicate via the one or more second cells (e.g.,may transmit uplink signals/channels or may receive downlinksignals/channels via the one or more second cells). In an example, inresponse to transmission of the first indication, the wireless devicemay switch from the one or more first cells to the one or more secondcells. The communication via the one or more second cells and/orswitching to the one or more second cells may be based on the secondconfiguration parameters of the one or more second cells.

In an example embodiment as shown in FIG. 20 , the wireless device mayreceive a first acknowledgement in response to transmission of the firstindication indicating successful reception (e.g., by the first BS) ofthe first indication. The wireless device may communicate via the one ormore second cells and/or switch from the one or more first cells to theone or more second cells in response to reception of the firstacknowledgement. For example, the wireless device may communicate viathe one or more second cells and/or switch from the one or more firstcells to the one or more second cells on/after an offset from a firsttiming of reception of the first acknowledgement. In an example, theoffset may be in a number of symbols or in a number of slots. In anexample, the offset may be pre-configured. In an example, the offset maybe configurable, and the wireless device may receive a configurationparameter indicating the offset.

In an example, the first acknowledgement may be a HARQ acknowledgement.For example, in case the first indication is via a MAC CE multiplexed ina transport block, the first acknowledgement may indicate successfulreception of the transport block (e.g., by the first BS). The wirelessdevice may communicate via the one or more second cells and/or switchfrom the one or more first cells to the one or more second cells inresponse to reception of the first HARQ acknowledgement. For example,the wireless device may communicate via the one or more second cellsand/or switch from the one or more first cells to the one or more secondcells on/after an offset from a first timing of reception of the firstHARQ acknowledgement. In an example, the offset may be in a number ofsymbols or in a number of slots. In an example, the offset may bepre-configured. In an example, the offset may be configurable, and thewireless device may receive a configuration parameter indicating theoffset.

In an example, the first acknowledgement may be via a second MAC CE. Forexample, the second MAC CE may have a zero payload and an LCIDassociated with the second MAC CE may indicate that the second MAC CE isfor an acknowledgement of the first indication. The wireless device maycommunicate via the one or more second cells and/or switch from the oneor more first cells to the one or more second cells in response toreception of the second MAC CE. For example, the wireless device mayinitiate the handover on/after an offset from a first timing ofreception of the second MAC CE. In an example, the offset may be in anumber of symbols or in a number of slots. In an example, the offset maybe pre-configured. In an example, the offset may be configurable, andthe wireless device may receive a configuration parameter indicating theoffset.

In an example embodiment, the wireless device may receive a secondindication from the first base station in response to transmitting thefirst indication. The second indication may indicate one or more thirdcells of the one or more second cells. The one or more third cells maybe a subset of the one or more second cells and the base station maydetermine/select the one or more third cells from the one or more secondcells based on some criteria such as channel conditions of the one ormore third cells, etc. In an example, the second indication may be basedon a DCI transmitted via an uplink control channel. In an example, thesecond indication may be via a MAC CE. In an example, the wirelessdevice may transmit an acknowledgement (e.g., a HARQ acknowledgement ora MAC CE) in response to receiving the second indication.

In an example embodiment as shown in FIG. 21 , the wireless device mayobtain one or more timing advance (TA) values (e.g., one or more TAvalues associated with the one or more second cells) prior to theinitiating the one or more handover processes (e.g., the handover fromthe one or more first cells of the first BS to the one or more secondcells of the second BS) and/or prior to switching from the one or morefirst cells to the one or more second cells and/or prior tocommunicating via the one or more second cells. In an example, the oneor more second cells may be in the same timing advance group (TAG). Inexample embodiments as shown in FIG. 31 and FIG. 32 , obtaining the oneor more TA values may comprise performing one or more random accessprocesses (e.g., via the one or more second cells). The obtaining theone or more TA values may comprise transmitting one or more randomaccess preambles (e.g., via the one or more second cells) and mayreceive (e.g., from the first base station) the one or more TA values.In an example, the wireless device may transmit the one or more randomaccess preambles via the one or more second cells to the second BS andthe second BS may determine the one or more TA values. The second BS maytransmit (e.g., via an application protocol message, e.g., an Xnmessage) the determined one or more TA values to the first BS and thefirst BS may transmit the one or more TA values to the wireless device.In an example, receiving the one or more TA values may be based on oneor more MAC CEs. The one or more MAC CEs may be based on a first formatindicating that the one or more MAC CEs are associated with/used inL1/L2 based mobility/switching. In an example, the one or more MAC CEsmay be associated with a first logical channel identifier (LCID)indicating that the one or more MAC CEs are associated with/used inL1/L2 based mobility/switching. In an example, a MAC CE in the one ormore MAC CEs may comprise a field (e.g., a TAG ID field) with a valueindicating that the MAC CE is associated with/used in L1/L2 basedmobility/switching.

Example uplink control information (UCI) or MAC CEs (e.g., MAC CEformats) used for the first indication (e.g., first indication of theone or more second cells from the wireless device to the first BS) areshown in FIG. 22 , FIG. 23 , and FIG. 24 . For example, as shown in FIG.22 , the number of the one or more second cells may be N. The UCI or theMAC CE used for transmission of the first indication may comprise aplurality of fields (e.g., N fields, e.g., a bitmap comprising N bits).Each field in the plurality of fields may correspond to a correspondingcell in the one or more second cells. For example, the rightmost fieldof the UCI/MAC CE may correspond to Cell_0 that corresponds to a cell ina plurality of cells that has the lowest cell index/ID of the cellindexes/IDs of the plurality of cells. The field adjacent to therightmost field of the UCI/MAC CE may correspond to Cell_1 thatcorresponds to a cell in a plurality of cells that has the second lowestcell index/ID of the cell indexes/IDs of the plurality of cells. Theleftmost field of the UCI/MAC CE may correspond to Cell_(N−1) thatcorresponds to a cell in a plurality of cells that has the highest cellindex/ID of the cell indexes/IDs of the plurality of cells. A value of afield may indicate that the corresponding cell is activated ordeactivated for L1/L2 based handover/switching. A value of one mayindicate that the corresponding cell is activated for L1/L2 basedhandover/switching. A value of zero may indicate that the correspondingcell is deactivated for L1/L2 based handover/switching. In an example,as shown in FIG. 22 , the first indication may be based on a MAC CEformat with a fixed length. For example, as shown in FIG. 23 , theUCI/MAC CE used for transmission of first indication may be comprise oneor more fields, wherein a value of a field in the one or more fields mayindicate an identifier/index of a cell/cell group. The presence of theidentifier/index of a cell/cell group may indicate activation of thehandover/switching for the cell/cell group corresponding to theidentifier/index of a cell/cell group. In an example, as shown in FIG.23 , the first indication may be based on a MAC CE format with avariable length. For example, as shown in FIG. 24 , the UCI/MAC CE usedfor transmission of first indication may comprise a plurality of fields.A first field, in the plurality of fields, may indicate anidentifier/index of a cell/cell group and second field, in the pluralityof fields, may have a value indicating whether the correspondingcell/cell group is activated or deactivated. For example, a value of onemay indicate that the corresponding cell/cell group is activated a valueof one may indicate that the corresponding cell/cell group is activatedand a value of zero may indicate that the corresponding cell/cell groupis deactivated a value of one may indicate that the correspondingcell/cell group is activated. In an example, as shown in FIG. 24 , thefirst indication may be based on a MAC CE format with a variable length.

In example embodiments as shown in FIG. 25 , FIG. 26 and FIG. 27 , thewireless device may receive a first indication of handover/switchingfrom the one or more first cells to the one or more second cells. In anexample, the first BS may make a determination (e.g., based on themeasurement results received from the wireless device) ofhandover/switching from the one or more first cells to the one or moresecond cells and may transmit the first indication based on thedetermination. In an example, the base station may make a selectin(e.g., based on the measurement results received from the wirelessdevice) of the one or more second cells for handover/switching from theone or more first cells to the one or more second cells and may transmitthe first indication that the first base station has made the selection.

In an example, the first indication may be via physical layer signalingor may be via MAC layer signaling.

In an example, in case the first indication is via physical layersignaling, the physical layer signaling may be via downlink controlinformation (e.g., DCI to be transmitted via a downlink control channel)or via a downlink signal (e.g., via a downlink reference signal such asSSB, CSI-RS, DMRS, etc.). In an example a sequence associated with thedownlink signal (e.g., a sequence (e.g., a sequence number) associatedwith the downlink signal, e.g., SSB, CSI-RS or DMRS) may be used for thefirst indication. The wireless device may receive configurationparameters for reception of (e.g., for determining radio resources forreception of) the first indication via the downlink control channel(e.g., for transmission of the DCI) or based on the downlink signal.

In an example, in case the first indication is MAC layer signaling, theMAC layer signaling for transmission of the first indication may be viaa first MAC CE (e.g., a downlink MAC CE). In an example, the first MACCE may have a first format associated with L1/L2 basedhandover/switching. In an example, the first MAC CE may be associatedwith a first LCID that is associated with the L1/L2 basedhandover/switching. The first MAC CE may be multiplexed in a transportblock and the wireless device may receive the transport block basedon/via a downlink shared/data channel.

In an example, the one or more first cells may be associatedwith/of/provided by the first BS and the one or more second cells may beassociated with/of/provided by the second BS. The first indication,transmitted by the first BS and received by the wireless device, mayindicate the handover from the one or more first cells of the first BSto the one or more second cells of the second BS. In response toreceiving the first indication, the wireless device may initiate thehandover from the one or more first cells of the first BS to the one ormore second cells of the second BS. In an example, the wireless devicemay initiate the handover based on second configuration parameters ofthe one or more second cells (e.g., received prior to the indication).

In an example embodiment as shown in FIG. 26 , the wireless device maytransmit a first acknowledgement in response to reception of the firstindication indicating successful reception (e.g., by the wirelessdevice) of the first indication. The wireless device may initiate thehandover from the one or more first cells of the first BS to the one ormore second cells of the second BS in response to transmission of thefirst acknowledgement. For example, the wireless device may initiate thehandover on/after an offset from a first timing of transmission of thefirst acknowledgement. In an example, the offset may be in a number ofsymbols or in a number of slots. In an example, the offset may bepre-configured. In an example, the offset may be configurable, and thewireless device may receive a configuration parameter indicating theoffset.

In an example, the first acknowledgement may be a HARQ acknowledgement.For example, in case the first indication is via a MAC CE multiplexed ina transport block, the first acknowledgement may indicate successfulreception of the transport block (e.g., by the wireless device). Thewireless device may initiate the handover from the one or more firstcells of the first BS to the one or more second cells of the second BSin response to transmission of the first HARQ acknowledgement. Forexample, the wireless device may initiate the handover on/after anoffset from a first timing of transmission of the first HARQacknowledgement. In an example, the offset may be in a number of symbolsor in a number of slots. In an example, the offset may bepre-configured. In an example, the offset may be configurable, and thewireless device may receive a configuration parameter indicating theoffset.

In an example, the first acknowledgement may be via a second MAC CE. Forexample, the second MAC CE may have a zero payload and an LCIDassociated with the second MAC CE may indicate that the second MAC CE isfor an acknowledgement of the first indication. The wireless device mayinitiate the handover from the one or more first cells of the first BSto the one or more second cells of the second BS in response totransmission of the second MAC CE. For example, the wireless device mayinitiate the handover on/after an offset from a first timing oftransmission of the second MAC CE. In an example, the offset may be in anumber of symbols or in a number of slots. In an example, the offset maybe pre-configured. In an example, the offset may be configurable, andthe wireless device may receive a configuration parameter indicating theoffset.

In an example, the initiating the handover from the one or more firstcells of the first BS to the one or more second cells of the second BSmay comprise initiating one or more random access processes comprisingtransmitting one or more random access preambles via the one or moresecond cells. The initiating the one or more random access processes maybe based on second configurations parameters of the one or more secondcells (e.g., random access configuration parameters indicating randomaccess occasions/parameters).

In an example, in response to reception of the first indication, thewireless device may communicate via the one or more second cells (e.g.,may transmit uplink signals/channels or may receive downlinksignals/channels via the one or more second cells). In an example, inresponse to reception of the first indication, the wireless device mayswitch from the one or more first cells to the one or more second cells.The communication via the one or more second cells and/or switching tothe one or more second cells may be based on the second configurationparameters of the one or more second cells.

In an example embodiment as shown in FIG. 26 , the wireless device maytransmit a first acknowledgement in response to reception of the firstindication indicating successful reception (e.g., by the wirelessdevice) of the first indication. The wireless device may communicate viathe one or more second cells and/or switch from the one or more firstcells to the one or more second cells in response to transmission of thefirst acknowledgement. For example, the wireless device may communicatevia the one or more second cells and/or switch from the one or morefirst cells to the one or more second cells on/after an offset from afirst timing of transmission of the first acknowledgement. In anexample, the offset may be in a number of symbols or in a number ofslots. In an example, the offset may be pre-configured. In an example,the offset may be configurable, and the wireless device may receive aconfiguration parameter indicating the offset.

In an example, the first acknowledgement may be a HARQ acknowledgement.For example, in case the first indication is via a MAC CE multiplexed ina transport block, the first acknowledgement may indicate successfulreception of the transport block (e.g., by the wireless device). Thewireless device may communicate via the one or more second cells and/orswitch from the one or more first cells to the one or more second cellsin response to transmission of the first HARQ acknowledgement. Forexample, the wireless device may communicate via the one or more secondcells and/or switch from the one or more first cells to the one or moresecond cells on/after an offset from a first timing of transmission ofthe first HARQ acknowledgement. In an example, the offset may be in anumber of symbols or in a number of slots. In an example, the offset maybe pre-configured. In an example, the offset may be configurable, andthe wireless device may receive a configuration parameter indicating theoffset.

In an example, the first acknowledgement may be via a second MAC CE. Forexample, the second MAC CE may have a zero payload and an LCIDassociated with the second MAC CE may indicate that the second MAC isfor an acknowledgement of the first indication. The wireless device maycommunicate via the one or more second cells and/or switch from the oneor more first cells to the one or more second cells in response totransmission of the second MAC CE. For example, the wireless device mayinitiate the handover on/after an offset from a first timing oftransmission of the second MAC CE. In an example, the offset may be in anumber of symbols or in a number of slots. In an example, the offset maybe pre-configured. In an example, the offset may be configurable, andthe wireless device may receive a configuration parameter indicating theoffset.

In an example embodiment as shown in FIG. 27 , the wireless device mayobtain one or more timing advance (TA) values (e.g., one or more TAvalues associated with the one or more second cells) prior to theinitiating the one or more handover processes (e.g., the handover fromthe one or more first cells of the first BS to the one or more secondcells of the second BS) and/or prior to switching from the one or morefirst cells to the one or more second cells and/or prior tocommunicating via the one or more second cells. In example embodimentsas shown in FIG. 31 and FIG. 32 , obtaining the one or more TA valuesmay comprise performing one or more random access processes (e.g., viathe one or more second cells). The obtaining the one or more TA valuesmay comprise transmitting one or more random access preambles (e.g., viathe one or more second cells) and may receive (e.g., from the first basestation) the one or more TA values. In an example as shown in FIG. 32 ,the wireless device may transmit the one or more random access preamblesvia the one or more second cells to the second BS and the second BS maydetermine the one or more TA values. The second BS may transmit (e.g.,via an application protocol message, e.g., an Xn message) the determinedone or more TA values to the first BS and the first BS may transmit theone or more TA values to the wireless device. In an example, receivingthe one or more TA values may be based on one or more MAC CEs. The oneor more MAC CEs may be based on a first format indicating that the oneor more MAC CEs are associated with/used in L1/L2 basedmobility/switching. In an example, the one or more MAC CEs may beassociated with a first logical channel identifier (LCID) indicatingthat the one or more MAC CEs are associated with/used in L1/L2 basedmobility/switching. In an example, a MAC CE in the one or more MAC CEsmay comprise a field (e.g., a TAG ID field) with a value indicating thatthe MAC CE is associated with/used in L1/L2 based mobility/switching.

Example downlink control information (DCI) or MAC CEs (e.g., MAC CEformats) used for the first indication (e.g., first indication of theone or more second cells from the first BS to the wireless device) areshown in FIG. 28 , FIG. 29 , and FIG. 30 . For example, as shown in FIG.28 , the number of the one or more second cells may be N. The DCI or theMAC CE used for transmission of the first indication may comprise aplurality of fields (e.g., N fields, e.g., a bitmap comprising N bits).Each field in the plurality of fields may correspond to a correspondingcell in a plurality of cells (e.g., the one or more second cells). Forexample, the rightmost field of the DCI/MAC CE may correspond to Cell_0that corresponds to a cell in a plurality of cells that has the lowestcell index/ID of the cell indexes/IDs of the plurality of cells. Thefield adjacent to the rightmost field of the DCI/MAC CE may correspondto Cell_1 that corresponds to a cell in a plurality of cells that hasthe second lowest cell index/ID of the cell indexes/IDs of the pluralityof cells. The leftmost field of the DCI/MAC CE may correspond toCell_(N−1) that corresponds to a cell in a plurality of cells that hasthe highest cell index/ID of the cell indexes/IDs of the plurality ofcells. A value of a field may indicate that the corresponding cell isactivated or deactivated for L1/L2 based handover/switching. A value ofone may indicate that the corresponding cell is activated for L1/L2based handover/switching. A value of zero may indicate that thecorresponding cell is deactivated for L1/L2 based handover/switching. Inan example, as shown in FIG. 28 , the first indication may be based on aMAC CE format with a fixed length. For example, as shown in FIG. 29 ,the DCI/MAC CE used for transmission of first indication may be compriseone or more fields, wherein a value of a field in the one or more fieldsmay indicate an identifier/index of a cell/cell group. The presence ofthe identifier/index of a cell/cell group may indicate activation of thehandover/switching for the cell/cell group corresponding to theidentifier/index of a cell/cell group. In an example, as shown in FIG.29 , the first indication may be based on a MAC CE format with avariable length. For example, as shown in FIG. 30 , the DCI/MAC CE usedfor transmission of first indication may be comprise a plurality offields. A first field, in the plurality of fields, may indicate anidentifier/index of a cell/cell group and a second field, in theplurality of fields, may have a value indicating whether thecorresponding cell/cell group is activated or deactivated for L1/L2based handover/switching. For example, a value of one may indicate thatthe corresponding cell/cell group is activated for L1/L2 basedhandover/switching and a value of zero may indicate that thecorresponding cell/cell group is deactivated for L1/L2 basedhandover/switching. In an example, as shown in FIG. 29 , the firstindication may be based on a MAC CE format with a variable length.

In an example embodiment as shown in FIG. 33 , a wireless device maytransmit a capability message comprising one or more capability IEs. Theone or more capability IEs may indicate that the wireless device iscapable of and/or supports cell switching or handover based on L1/L2signaling (e.g., physical layer or MAC layer signaling). The wirelessdevice may receive, in response to transmission of the capabilitymessage, the first configuration parameters of the one or more firstcells and the second configuration parameters of the one or more secondcells wherein the handover/switching from the one or more first cells tothe one or more second cells based on L1/L2 signaling may beenabled/configured. The wireless device may initiate handover/switchingfrom the one or more first cells to the one or more second cells basedon L1/L2 signaling in response to receiving the first configurationparameters and the second configuration parameters.

In example embodiments as shown in FIG. 34 and FIG. 35 , the first BSmay transmit a first application protocol message (e.g., a first Xnmessage) indicating a request for configuration of one or more cells forhandover/inter-cell mobility based on L1/L2 signaling (e.g., physicallayer or MAC layer signaling). The first application protocol messagemay comprise one or more first IEs indicating the request. In anexample, transmission of the first application protocol message from thefirst BS to the second BS may be based on/in response to the first BSreceiving, from the wireless device, a capability message comprising oneor more capability IEs indicating that the wireless device supports/iscapable of handover/inter-cell mobility based on the L1/L2 signaling.

In response to transmission of the first application protocol message tothe second BS, the first BS may receive a second application protocolmessage. In an example embodiment as shown in FIG. 34 , the secondapplication protocol message may indicate accepting or denying therequest. For example, the second application protocol message maycomprise one or more second IEs indicating accepting or denying therequest. For example, one or more first values of the one or more secondIEs may indicate accepting the request and one or more second values ofthe one or more second IEs may indicate denying the request. In anexample embodiment as shown in FIG. the second application protocolmessage may comprise (e.g., based on the request being accepted by thesecond BS) configurations/configuration parameters of the one or morecells for handover/inter-cell mobility based on the L1/L2 signaling.

In an example embodiment, a wireless device may receive, from a firstbase station, first configuration parameters, second configurationparameters, and third configuration parameters. The first configurationparameters may be for one or more first cells. The second configurationparameters may be for one or more second cells. The third configurationparameters may be for measurements. The wireless device may transmit tothe first base station and in response to the measurements, a firstindication of handover/switching from the one or more first cells to oneor more second cells.

In an example, the one or more first cells may be of/associated with thefirst base station. The one or more second cells may be of/associatedwith a second base station. In an example, the first indication may befor handover from the one or more first cells of the first base stationto the one or more second cells of the second base station. In anexample, the wireless device may initiate, in response to transmittingthe first indication, one or more handover processes. In an example, theinitiating the one or more handover processes may be based on the secondconfiguration parameters of the one or more second cells. In an example,the wireless device may receive a first acknowledgement, in response totransmitting the first indication. The initiating the one or morehandover processes may be in response to receiving the firstacknowledgement. In an example, the first acknowledgement may be basedon a hybrid automatic repeat request (HARQ) acknowledgement. In anexample, the HARQ acknowledgement may indicate successful reception of atransport block comprising the first indication (e.g., in case the firstindication is via a MAC CE multiplexed in the transport block). In anexample, the initiating the one or more handover processes may beon/started on or after an offset (e.g., a pre-configured offset or aconfigurable offset) from a timing of the transmission of the firstacknowledgement. In an example, the offset may be in a number of symbolsor in a number of slots. In an example, the offset may be based on anumerology/subcarrier spacing. In an example, the first acknowledgementmay be a second MAC CE (e.g., a MAC CE with zero payload). In anexample, the one or more handover processes may comprise transmittingone or more random access preambles via the one or more second cells.

In an example, the first indication may be via physical layer signaling(e.g., uplink control information, transmitted for example via an uplinkcontrol channel) or MAC layer signaling (e.g., via one or more MAC CEs).

In an example, the first indication may be that the wireless device hasmade a determination to switch from the one or more first cells to theone or more second cells. In an example, the wireless device maycommunicate, in response to transmitting the first indication, via theone or more second cells. In an example, the wireless device may switch,in response to transmitting the first indication, from the one or morefirst cells to the one or more second cells. In an example, thecommunicating via the one or more second cells or switching from the oneor more first cells to the one or more second cells may be based on thesecond configuration parameters of the one or more second cells. In anexample, the wireless device may receive a first acknowledgement inresponse to the transmitting the first indication. The communicating viathe one or more second cells or switching from the one or more firstcells to the one or more second cells may be in response to thereceiving the first acknowledgement. In an example, the firstacknowledgement may be based on a hybrid automatic repeat request (HARQ)acknowledgement. In an example, the HARQ acknowledgement may indicatesuccessful reception of a transport block comprising the firstindication (e.g., in case the first indication is via a MAC CEmultiplexed in the transport block). In an example, the communicatingvia the one or more second cells or switching from the one or more firstcells to the one or more second cells may be on/started on or after anoffset (e.g., a pre-configured offset or a configurable offset) from atiming of the transmission of the first acknowledgement. In an example,the offset may be in a number of symbols or in a number of slots. In anexample, the offset may be based on a numerology/subcarrier spacing. Inan example, the first acknowledgement may be based on a second MAC CE(e.g., a MAC CE with zero payload).

In an example, the first indication may be that the wireless device hasmade a selection of the one or more second cells for thehandover/switching from the one or more first cells to the one or moresecond cells.

In an example, the first indication may be based on first uplink controlinformation. In an example, the transmitting the first uplink controlinformation may be via an uplink control channel. In an example, thewireless device may receive configuration parameters indicating radioresources for transmission of the first uplink control information(e.g., via the uplink control channel). In an example, the transmittingthe first uplink control information may be via an uplink shared/datechannel. In an example, the wireless device may receive an uplink grantindicating radio resources for transmission of a transport block via theuplink shared channel. The transmitting the first uplink controlinformation may be based on the radio resources indicated by the uplinkgrant.

In an example, the first indication may be based on a physical layersignal. In an example, the physical layer signal may be a demodulationreference signal (DMRS). In an example, the first indication may be asequence associated with the physical layer signal (e.g., a sequencenumber associated with the DMRS). In an example, the physical layersignal (e.g., DMRS) may be transmitted via uplink shared/data channelresources.

In an example, the first indication may be based on a first mediumaccess control (MAC) control element (CE). In an example, the first MACCE may be associated with a first logical channel identifier (LCID)associated with L1/L2 based handover/signaling. In an example, the firstMAC CE may be multiplexed in a transport block. Transmitting thetransport block may be based on/via an uplink shared/data channel.

In an example, the wireless device may receive from the first basestation, a second indication of one or more third cells of the one ormore second cells. In an example, the second indication may be based ona downlink control information (DCI). In an example, the wireless devicemay receive the downlink control information is via a downlink controlchannel. In an example, the second indication may be based on a secondMAC CE. In an example, the wireless device may transmit a secondacknowledgment in response to receiving the second indication. In anexample, the second acknowledgement may be based on a hybrid automaticrepeat request (HARQ) acknowledgement. In an example, the secondacknowledgement may be based on a third MAC CE.

In an example, the one or more second cells may be in the same timingadvance group (TAG).

In an example, the wireless device may obtain one or more timing advance(TA) values (e.g., associated with the one or more second cells) priorto the initiating the one or more handover processes and/or prior to thecommunicating via the one or more second cells. In an example, obtainingthe one or more TA values may comprises performing one or more randomaccess processes (e.g., via the one or more second cells). In anexample, obtaining the one or more TA values may comprise transmittingone or more random access preambles and receiving the one or more TAvalues from the first BS. In an example, the second base station maytransmit the one or more TA values to the first base station and thefirst base station may transmit the one or more TA values to thewireless device. In an example, the receiving the one or more TA valuesmay be via one or more MAC CEs. In an example, the one or more MAC CEsmay be associated with a first format used for transmission of one ormore TAs used in L1/L2 based mobility/switching. In an example, the oneor more MAC CEs may be associated with a first logical channelidentifier (LCID) indicating that the one or more MAC CEs are used fortransmission of one or more TAs used in L1/L2 based mobility/switching.In an example, a MAC CE, in the one or more MAC CEs, may comprise afield (e.g., a TAG ID field) indicating that the MAC CE is used intransmission of a TA used in L1/L2 based mobility/switching.

In an example, the wireless device may transmit a message (e.g., acapability message) comprising one or more capability informationelements (IEs) with one or more values indicating that the wirelessdevice supports L1/L2 based (e.g., based on physical layer or MAC layersignaling) mobility (e.g., inter-cell handover) and/or switching. In anexample, the receiving the second configuration parameters of the one ormore second cells for L1/L2 based mobility (e.g., mobility based onphysical layer or MAC layer signaling, e.g., inter-cell handover) and/orswitching is in response to/based on the one or more values of the oneor more capability IEs indicating that the wireless device supportsL1/L2 based mobility and/or switching.

In an example embodiment, a wireless device may receive, from a firstbase station, first configuration parameters, second configurationparameters and third configuration parameters. The first configurationparameters may be for one or more first cells. The second configurationparameters may be for one or more second cells. The third configurationparameters may be for measurements. The wireless device may transmit tothe first base station and based on the third configuration parameters,the measurements comprising first measurements associated with the oneor more second cells. The wireless device may receive a first indicationof handover/switching from the one or more first cells to one or moresecond cells.

In an example, the one or more first cells may be of/associated with thefirst base station. The one or more second cells may be of/associatedwith a second base station. In an example, the first indication may befor handover from the one or more first cells of the first base stationto the one or more second cells of the second base station. In anexample, the wireless device may initiate, in response to receiving thefirst indication, one or more handover processes. In an example, theinitiating the one or more handover processes may be based on the secondconfiguration parameters of the one or more second cells. In an example,the wireless device may transmit a first acknowledgement in response tothe receiving the first indication. The initiating the one or morehandover processes may be in response to the transmitting the firstacknowledgement. In an example, the first acknowledgement may be basedon a hybrid automatic repeat request (HARQ) acknowledgement. In anexample, the HARQ acknowledgement may indicate successful reception of atransport block comprising the first indication (e.g., in case the firstindication is via a MAC CE multiplexed in a transport block). In anexample, the initiating the one or more handover processes may beon/started on or after an offset (e.g., a pre-configured offset or aconfigurable offset) from a timing of the reception of the firstacknowledgement. In an example, the offset may be in a number of symbolsor in a number of slots. In an example, the offset may be based on anumerology/subcarrier spacing. In an example, the first acknowledgementmay be based on a second MAC CE (e.g., a MAC CE with zero payload). Inan example, the one or more handover processes may comprise transmittingone or more random access preambles via the one or more second cells.

In an example, the first indication may be via physical layer signaling(e.g., downlink control information, received for example via a downlinkcontrol channel) or MAC layer signaling (e.g., via one or more MAC CEs).

In an example, the first indication may indicate/instruct switching fromthe one or more first cells to the one or more second cells. In anexample, the wireless device may communicate, in response to receivingthe first indication, via the one or more second cells. In an example,the wireless device may switch, in response to receiving the firstindication, from the one or more first cells to the one or more secondcells. In an example, the communicating via the one or more second cellsor switching from the one or more first cells to the one or more secondcells may be based on the second configuration parameters of the one ormore second cells. In an example, the wireless device may transmit afirst acknowledgement in response to the receiving the first indication,wherein the communicating via the one or more second cells or switchingfrom the one or more first cells to the one or more second cells may bein response to the transmitting the first acknowledgement. In anexample, the first acknowledgement may be based on a hybrid automaticrepeat request (HARQ) acknowledgement. In an example, the HARQacknowledgement may indicate successful reception of a transport blockcomprising the first indication (e.g., in case the first indication isvia a MAC CE multiplexed in the transport block). In an example, thecommunicating via the one or more second cells or switching from the oneor more first cells to the one or more second cells may be on/started onor after an offset (e.g., a pre-configured offset or a configurableoffset) from a timing of the transmission of the first acknowledgement.In an example, the offset may be in a number of symbols or in a numberof slots. In an example, the offset may be based on anumerology/subcarrier spacing. In an example, the first acknowledgementmay be based on a second MAC CE (e.g., a MAC CE with zero payload).

In an example, the first indication may be that the base station hasmade a selection of the one or more second cells for thehandover/switching from the one or more first cells to the one or moresecond cells.

In an example, the first indication may be based on first downlinkcontrol information. In an example, the receiving the first downlinkcontrol information may be via a downlink control channel. In anexample, the wireless device may receive configuration used fortransmission of the first downlink control information (e.g., via thedownlink control channel). In an example, the first downlink controlinformation may be associated with a first format that is associatedwith/used in L1/L2 based handover/switching. In an example, the firstdownlink control information may be associated with a first format basedon being associated with/used in L1/L2 based handover/switching. In anexample, the first downlink control information may be associated with afirst RNTI that is associated with/used in L1/L2 basedhandover/switching. In an example, the first downlink controlinformation may be associated with a first RNTI based on beingassociated with/used in L1/L2 based handover/switching. In an example,the first downlink control information may comprise a field with a firstvalue indicating that the first downlink control information isassociated with/used in L1/L2 based handover/switching. In an example,the first downlink control information may comprise a field with a firstvalue based on the first downlink control information being associatedwith/used in L1/L2 based handover/switching. In an example, the firstindication may be based on a physical layer signal. In an example, thephysical layer signal may be a demodulation reference signal (DMRS). Inan example, the first indication may be based on a sequence associatedwith the physical layer signal (e.g., a sequence number associated withDMRS). In an example, the physical layer signal (e.g., DMRS) may betransmitted via uplink shared/data channel resources.

In an example, the first indication may be based on a first mediumaccess control (MAC) control element (CE). In an example, the first MACCE may be associated with a first logical channel identifier (LCID) thatis associated with L1/L2 based handover/switching. In an example, thefirst MAC CE may be associated with a first logical channel identifier(LCID) based on the first MAC CE being associated/used in L1/L2 basedhandover/switching. In an example, the first MAC CE may be multiplexedin a transport block. Receiving the transport block may be based on/viaa downlink shared/data channel.

In an example, the one or more second cells may be in the same timingadvance group (TAG).

In an example, the wireless device may obtain one or more timing advance(TA) values (e.g., associated with the one or more second cells) priorto the initiating the one or more handover processes or prior to thecommunicating via the one or more second cells. In an example, theobtaining the one or more TA values may comprise performing one or morerandom access processes (e.g., via the one or more second cells). In anexample, the obtaining the one or more TA values may comprisetransmitting one or more random access preambles and receiving the oneor more TA values from the first BS. In an example, the second BS maytransmit the one or more TA values to the first BS and the first BS maytransmit the one or more TA values to the wireless device. In anexample, the receiving the one or more TA values may be via one or moreMAC CEs. In an example, the one or more MAC CEs may be associated with afirst format used for transmission of one or more TAs used in L1/L2based mobility/switching. In an example, the one or more MAC CEs may beassociated with a first logical channel identifier (LCID) indicatingthat the one or more MAC CEs are used for transmission of one or moreTAs used in L1/L2 based mobility/switching. In an example, a MAC CE, inthe one or more MAC CEs, may comprise a field (e.g., a TAG ID field)indicating that the MAC CE is used in transmission of a TA used in L1/L2based mobility/switching.

In an example, the wireless device may transmit a message (e.g., acapability message) comprising one or more capability informationelements (IEs) with one or more values indicating that the wirelessdevice supports L1/L2 based (e.g., based on physical layer or MAC layersignaling) mobility (e.g., inter-cell handover) and/or switching. In anexample, the receiving the second configuration parameters of the one ormore second cells for L1/L2 based mobility (e.g., mobility based onphysical layer or MAC layer signaling, e.g., inter-cell handover) and/orswitching is in response to/based on the one or more values of the oneor more capability IEs indicating that the wireless device supportsL1/L2 based mobility and/or switching.

In an example embodiment, a first base station (BS) may transmit to asecond BS, a first message (e.g., a first application protocol message)indicating (e.g., comprising one or more information elements (IEs)indicating) a request for parameters associated with L1/L2 basedmobility/handover (e.g., configuration parameters of one or more cellsof the second BS for L1/L2 based mobility, e.g., mobility based onphysical layer and/or MAC layer signaling) for a wireless device. Thefirst BS may receive from the second BS in response to the transmittingthe first message, a second message (e.g., a second application protocolmessage) indicating accepting or denying the request.

In an example, based on the request being accepted by the second BS, thefirst BS may receive, from the second BS, configuration parameters ofone or more cells of the second BS for L1/L2 based mobility (e.g.,mobility based on physical layer and/or MAC layer signaling).

In an example, the first base station may receive from the wirelessdevice, one or more capability IEs indicating that the wireless devicesupports L1/L2 based mobility/handover (e.g., mobility/handover based onphysical layer and/or MAC layer signaling). The transmitting the firstmessage and/or including the one or more IEs in the first message may bebased on the wireless device supporting the L1/L2 basedmobility/handover.

In an example embodiment as shown in FIG. 36 , a wireless device maytransmit one or more measurement reports. The wireless device maytransmit the one or more measurement reports to a first base station.The wireless device may transmit the one or more measurement reports asuplink control information (UCI) transmitted semi-persistently on PUSCHor as aperiodic report(s) on PUSCH or periodically/semi-persistently onPUCCH. The one or more measurement reports may comprise measurementresults associated with a second base station. In an example, themeasurements results may comprise SSB based L1-RSRP and/or CSI-RS basedL1-RSRP and/or may be based on L1-SINR.

The wireless device may determine a timing advance value associated withthe second cell. The wireless device may determine the timing advancevalue prior to receiving a cell switching/handover command (e.g., a cellswitch MAC CE). For example, the wireless device may determine thetiming advance value based on initiating a random access process. Thewireless device may initiate the random access process prior toreceiving the cell switching/handover command (e.g., the cell switch MACCE). In an example, the wireless device may initiate the random accessprocess based on and in response to receiving a PDCCH order, e.g., basedon receiving a DCI indicating initiation of the random access process.The PDCCH order may comprise or may be associated with one or moreparameters indicating that the random access process is for obtaining atiming advance value that is used in mobility based on L1/L2 signaling.The random access process may comprise transmitting at least one randomaccess preamble. The random access process may comprise transmitting atleast one random access preamble via the second cell (e.g., via randomaccess resources/occasions of the second cell). A base station receivingthe at least one random access preamble may determine the timing advancevalue. In an example, the base station receiving the at least one randomaccess preamble may transmit a message (e.g., a random access response(RAR) message) comprising a parameter indicating the timing advancevalue and the wireless may determine the timing advance value based onthe parameter in response to receiving the message (e.g., the randomaccess response (RAR) message). In an example, the wireless device maydetermine the timing advance value based on the cell switching/handovercommand (e.g., the cell switch MAC CE). The cell switching/handovercommand (e.g., the cell switch MAC CE) may comprise a field with a valueindicating the timing advance value. In an example, receiving the timingadvance value may be via the first cell. The wireless device maytransmit the at least one preamble via the first cell (e.g., the firstcell of the first base station) and may receive the timing advance valuevia the second cell (e.g., the second cell of the second base station).In an example, receiving the timing advance value may be based on a MACCE (e.g., a timing advance MAC CE).

The wireless device may receive configuration parameters of one or morecells as candidate cells for L1/L2 based mobility (e.g., inter-cellmobility). In an example, the configuration parameters of the one ormore cells may be full configuration parameters of the one or morecells. In an example, the configuration parameters of the one or morecells may be partial configuration parameters of the one or more cells.The one or more cells may comprise the second cell. In an example, theconfiguration parameters of the one or more cells may comprise randomaccess configuration parameters, e.g., random access configurationparameters for random access processes on the second cell, e.g., randomaccess configuration parameters of the second cell that are associatedwith obtaining time advance values for L1/L2 based mobility (e.g.,inter-cell mobility). The wireless device may initiate the random accessprocess based on the random access configuration parameters.

The wireless device may receive the cell switch/handover MAC CEindicating switching/handover from the first cell to the second cell.The wireless device may receive a transport block (e.g., via PDSCH)comprising the cell switch/handover MAC CE. In an example, the firstcell and the second cell may be provided by/associated with differentbase stations. The first cell may be provided by/associated with a firstbase station and the second cell may be provided by/associated with asecond base station. The cell switch/handover command/MAC CE mayindicate a handover from the first cell of the first base station to thesecond cell of the second base station. The wireless device may initiatea handover from the first cell of the first base station to the secondcell of the second base station in response to receiving the cellswitch/handover MAC CE. In an example, the first cell and the secondcell may be provide by/associated with the same base station. The cellswitch/handover command/MAC CE may indicate switching from the firstcell to the second cell, for example may indicate a SpCell change (e.g.,a primary cell (PCell) change or a PSCell change for a cell groupprovided by a secondary base station in case of dual connectivity)and/or change of an SCell. The wireless device may switch from the firstcell to the second cell, for example may change a SpCell (e.g., change aprimary cell (PCell) or change a PSCell for a cell group provided by asecondary base station in case of dual connectivity) and/or may changeof an SCell in response to receiving the cell switch/handovercommand/MAC CE.

In an example, the cell switch/handover command MAC CE may comprise afield with a value indicating switching to the second cell (e.g.,switching from the first cell to the second cell) and/or handover to thesecond cell (e.g., handover from the first cell to the second cell). Inan example, the cell switch/handover command/MAC CE may comprise a fieldwith a value indicating an identifier of the second cell. For example,the configuration parameters of the one or more cells, comprising thesecond cell and received prior to receiving the cell switch/handovercommand/MAC CE, may comprise a configuration parameter indicating theidentifier of the second cell (e.g., a cell index, e.g., an RRCconfigured cell identifier/index, a temporary cell identifier/indexconfigured by RRC, etc.).

In an example, the cell switch/handover command MAC CE may comprise afield with a value indicating switching to a cell group (e.g., switchingfrom the first cell group to the second cell group). The first cellgroup may comprise the first cell and the second cell group may comprisethe second cell. In an example, the cell switch/handover command/MAC CEmay comprise a field with a value indicating an identifier of the secondcell group. For example, the configuration parameters, received prior toreceiving the cell switch/handover command/MAC CE, may comprise aconfiguration parameter indicating the identifier of the second cellgroup (e.g., an RRC configured identifier/index of the second cellgroup, a temporary identifier/index of the second cell group configuredby RRC, etc.).

In an example, the cell switch/handover command/MAC CE may be a fixedlength MAC CE (e.g., irrespective of number of cells to which the cellswitching/handover is indicated). In an example, the cellswitch/handover command/MAC CE may be a variable length MAC CE (e.g.,based on the number of cells to which the cell switching/handover isindicated). The cell switch/handover MAC CE may be associated with anLCID that is associated with L1/L2 based/triggered inter-cell mobilityand indicates that the MAC CE is for/associated with L1/L2 based oninter-cell mobility. In an example, the cell switch/handover command/MACCE may comprise one or more fields. Each field of the one or more fieldsmay be associated with a corresponding cell. A value of a field in theone or more fields may indicate a switching or handover to the cellcorresponding to the field. In an example, the cell switch/handovercommand/MAC CE may comprise one or more bits. Each bit of the one ormore bits may be associated with a corresponding cell. A value of a bitin the one or more bits may indicate a switching or handover to the cellcorresponding to the bit.

In an example, the reception of the cell switch/handover command/MAC CEmay be based on the wireless device being capable of/supporting theL1/L2 signaling based cell switching/handover/inter-cell mobility. Thewireless device may transmit a capability message comprising one or morecapability information elements indicating that the wireless device iscapable of/supports cell switching and/or handover and/or inter-cellmobility based on L1/L2 signaling (e.g., a cell switch/handover MAC CE),e.g., L1/L2 triggered mobility. In response to transmitting thecapability message indicating that the wireless device is capableof/supports cell switching and/or handover and/or inter-cell mobilitybased on L1/L2 signaling (e.g., a cell switch/handover MAC CE), e.g.,L1/L2 triggered mobility, the wireless deice may receive configurationparameters of one or more cells (e.g., candidate cells) for cellswitching and/or handover and/or inter-cell mobility based on L1/L2signaling (e.g., a cell switch/handover MAC CE), e.g., L1/L2 triggeredmobility.

The wireless device may perform an uplink transmission on the secondcell based on the timing advance value and in response to receiving thecell switch/handover MAC CE. The wireless device may perform the uplinktransmission on the second cell based on the timing advance value and inresponse to the switching/handover to the second cell. The timing ofperforming/initiating the uplink transmission may be based on a timingof an acknowledgement (e.g., HARQ acknowledgement, e.g., ACK) associatedwith the transport block comprising the cell switch/handover MAC CE, forexample on or after the timing of transmitting the acknowledgement. Inan example, the timing of performing/initiating the uplink transmissionmay be an offset (e.g., a configurable offset, e.g., an RRC configurableoffset) from the timing of the acknowledgement. The offset may be in afirst number of symbols or in a first number of slots. The uplinktransmission may be based on the configuration parameters of the secondcell (e.g., the configuration parameters received prior to receiving thecell switch/handover MAC CE). The uplink transmission may be fortransmission via PUSCH, PRACH, etc.

In accordance with various exemplary embodiments in the presentdisclosure, a device (e.g., a wireless device, a base station and/oralike) may include one or more processors and may include memory thatmay store instructions. The instructions, when executed by the one ormore processors, cause the device to perform actions as illustrated inthe accompanying drawings and described in the specification. The orderof events or actions, as shown in a flow chart of this disclosure, mayoccur and/or may be performed in any logically coherent order. In someexamples, at least two of the events or actions shown may occur or maybe performed at least in part simultaneously and/or in parallel. In someexamples, one or more additional events or actions may occur or may beperformed prior to, after, or in between the events or actions shown inthe flow charts of the present disclosure.

FIG. 37 shows an example flow diagram in accordance with several ofvarious embodiments of the present disclosure. At 3710, a wirelessdevice may transmit at least one measurement report comprisingmeasurement results associated with a second cell. At 3720, the wirelessdevice may determine, based on initiating a random access process priorto receiving a cell switch medium access control (MAC) control element(CE), a timing advance value associated with the second cell. At 3730,the wireless device may receive the cell switch MAC CE indicatingswitching from a first cell to the second cell. At 3740, the wirelessdevice may perform an uplink transmission on the second cell based onthe timing advance value and in response to receiving the cell switchMAC CE.

In an example embodiment, the first cell may be provided by a first basestation. The second cell may be provided by a second base station. Thecell switch MAC CE, received at 3730, may indicate a handover from thefirst cell of the first base station to the second cell of the secondbase station. In an example embodiment, the wireless device may initiatea handover procedure from the first cell of a first base station to thesecond cell of a second base station in response to receiving the cellswitch MAC CE.

In an example embodiment, the first cell and the second cell may beprovided by the same base station.

In an example embodiment, in response to receiving the cell switch MACCE at 3730, the wireless device may switch from the first cell to thesecond cell.

In an example embodiment, initiating the random access process may be inresponse to receiving a physical downlink control channel (PDCCH) order.

In an example embodiment, the random access process may comprisetransmitting at least one random access preamble via the second cell. Inan example embodiment, the determining the timing advance value, at3720, may be based on receiving the timing advance value via the firstcell. In an example embodiment, the transmitting the at least one randomaccess preamble may be to a first base station and the receiving thetiming advance value may be from a second base station.

In an example embodiment, the receiving the timing advance value may bebased on receiving a MAC CE.

In an example embodiment, the wireless device may transmit one or morecapability messages indicating that the wireless device is capable ofand/or supports cell switching and/or handover and/or inter-cellmobility based on L1/L2 signaling (e.g., a cell switch MAC CE), e.g.,L1/L2 triggered mobility. In an example embodiment, the wireless devicemay receive, in response to transmitting the one or more capabilitymessages, configuration parameters of the second cell for cell switchingand/or handover and/or inter-cell mobility based on L1/L2 signaling(e.g., a cell switch MAC CE), e.g., L1/L2 triggered mobility. In anexample embodiment, the one or more capability messages may comprise oneor more capability information elements indicating that the wirelessdevice is capable of and/or supports cell switching and/or handoverand/or inter-cell mobility based on L1/L2 signaling (e.g., a cell switchMAC CE), e.g., L1/L2 triggered mobility.

In an example embodiment, the random access process may comprisetransmitting at least one random access preamble. The determining thetiming advance value, at 3720, may be in response to the transmittingthe at least one random access preamble.

In an example embodiment, the wireless device may receive configurationparameters of the second cell prior to receiving the cell switch MAC CE.In an example embodiment, the configuration parameters may compriserandom access configuration parameters. The random access process, basedon which the timing advance value is determined at 3720, may be based onthe random access configuration parameters. In an example embodiment,the performing the uplink transmission, at 3740, may be based on theconfiguration parameters.

In an example embodiment, the cell switch MAC CE may, received at 3730,may comprise a field with a value indicating a switching to the secondcell or handover to the second cell.

In an example embodiment, the cell switch MAC CE, received at 3730, maycomprise a field with a value indicating an identifier of the secondcell.

In an example embodiment, the cell switch MAC CE, received at 3730, maycomprise a field with a value indicating a switching to a cell group. Inan example embodiment, the cell group may comprise the second cell.

In an example embodiment, the cell switch MAC CE, received at 3730, maycomprise a field with a value indicating an identifier of a cell group.

In an example embodiment, the cell switch MAC CE, received at 3730, maycomprise one or more fields. Each field in the one or more fields may beassociated with a corresponding cell. A value (e.g., a value of one) ofa field in the one or more fields may indicate a switching/handing overto the cell corresponding to the field.

In an example embodiment, the cell switch MAC CE, received at 3730, maycomprise a field comprising one or more bits. Each bit in the one ormore bits may be associated with a corresponding cell. A value (e.g., avalue of one) of a bit in the one or more bits may indicate aswitching/handing over to the cell corresponding to the bit.

In an example embodiment, the cell switch MAC CE, received at 3730, mayhave a fixed length.

In an example embodiment, the cell switch MAC CE, received at 3730, mayhave a variable length.

In an example embodiment, the cell switch MAC CE, received at 3730, maybe associated with a logical channel identifier (LCID). The LCID mayindicate that the MAC CE is for cell switching/handover (L1/L2inter-cell mobility).

In an example embodiment, the receiving the cell switch MAC CE at 3730may be based on receiving a transport block comprising the cell switchMAC CE. In an example embodiment, the receiving the transport block maybe via a physical downlink shared channel (PDSCH).

In an example embodiment, performing the uplink transmission, at 3740,may be in response to/after transmitting an acknowledgement. In anexample, the acknowledgement may be a hybrid automatic repeat request(HARQ) acknowledgement. In an example embodiment, the acknowledgementmay indicate successful reception of a transport block comprising thecell switch MAC CE. In an example embodiment, performing the uplinktransmission, at 3740, may be on or after an offset from transmittingthe acknowledgement. In an example embodiment, the offset may be in afirst number of symbols or in a first number of slots. In an exampleembodiment, the wireless device may receive a configuration parameterindicating the offset.

FIG. 38 shows an example flow diagram in accordance with several ofvarious embodiments of the present disclosure. At 3810, a first basestation may transmit, to a second base station, a first messageindicating a request associated with handover/inter-cell mobility basedon L1/L2 signaling. At 3820, in response to transmitting the firstmessage, the first base station may receive a second message indicatingaccepting or denying the request.

In an example embodiment, at least one of the first message, transmittedat 3810, and the second message, received at 3820, may be an applicationprotocol message.

In an example embodiment, at least one of the first message, transmittedat 3810, and the second message, received at 3820, may be an Xn message.

In an example embodiment, the first message, transmitted at 3810, maycomprise one or more information elements indicating (e.g., with one ormore values indicating) the request.

In an example embodiment, the second message, received at 3820, maycomprise one or more information elements indicating (e.g., with one ormore values indicating) accepting or denying the request. In an exampleembodiment, one or more first values of the one or more informationelements may indicate accepting the request. One or more second valuesof the one or more information elements may indicate denying therequest.

In an example embodiment, the transmitting the first message/request at3810, by the first base station to the second base station, is inresponse to receiving, by the first base station from a wireless device,a capability message indicating that the wireless device is capable ofand/or supports handover/inter-cell mobility based on the L1/L2signaling.

In an example embodiment, the first base station may receive, from thesecond base station, configuration parameters of one or more cells forL1/L2 based/triggered handover/inter-cell mobility. In an exampleembodiment, the first base station may transmit the configurationparameters to the wireless device.

In an example embodiment, the first base station may transmit, to thewireless device, a cell switch medium access control (MAC) controlelement (CE) indicating handover to a first cell of the one or morecells.

Various exemplary embodiments of the disclosed technology are presentedas example implementations and/or practices of the disclosed technology.The exemplary embodiments disclosed herein are not intended to limit thescope. Persons of ordinary skill in the art will appreciate that variouschanges can be made to the disclosed embodiments without departure fromthe scope. After studying the exemplary embodiments of the disclosedtechnology, alternative aspects, features and/or embodiments will becomeapparent to one of ordinary skill in the art. Without departing from thescope, various elements or features from the exemplary embodiments maybe combined to create additional embodiments. The exemplary embodimentsare described with reference to the drawings. The figures and theflowcharts that demonstrate the benefits and/or functions of variousaspects of the disclosed technology are presented for illustrationpurposes only. The disclosed technology can be flexibly configuredand/or reconfigured such that one or more elements of the disclosedembodiments may be employed in alternative ways. For example, an elementmay be optionally used in some embodiments or the order of actionslisted in a flowchart may be changed without departure from the scope.

An example embodiment of the disclosed technology may be configured tobe performed when deemed necessary, for example, based on one or moreconditions in a wireless device, a base station, a radio and/or corenetwork configuration, a combination thereof and/or alike. For example,an example embodiment may be performed when the one or more conditionsare met. Example one or more conditions may be one or moreconfigurations of the wireless device and/or base station, traffic loadand/or type, service type, battery power, a combination of thereofand/or alike. In some scenarios and based on the one or more conditions,one or more features of an example embodiment may be implementedselectively.

In this disclosure, the articles “a” and “an” used before a group of oneor more words are to be understood as “at least one” or “one or more” ofwhat the group of the one or more words indicate. The use of the term“may” before a phrase is to be understood as indicating that the phraseis an example of one of a plurality of useful alternatives that may beemployed in an embodiment in this disclosure.

In this disclosure, an element may be described using the terms“comprises”, “includes” or “consists of” in combination with a list ofone or more components. Using the terms “comprises” or “includes”indicates that the one or more components are not an exhaustive list forthe description of the element and do not exclude components other thanthe one or more components. Using the term “consists of” indicates thatthe one or more components is a complete list for description of theelement. In this disclosure, the term “based on” is intended to mean“based at least in part on”. The term “based on” is not intended to mean“based only on”. In this disclosure, the term “and/or” used in a list ofelements indicates any possible combination of the listed elements. Forexample, “X, Y, and/or Z” indicates X; Y; Z; X and Y; X and Z; Y and Z;or X, Y, and Z.

Some elements in this disclosure may be described by using the term“may” in combination with a plurality of features. For brevity and easeof description, this disclosure may not include all possiblepermutations of the plurality of features. By using the term “may” incombination with the plurality of features, it is to be understood thatall permutations of the plurality of features are being disclosed. Forexample, by using the term “may” for description of an element with fourpossible features, the element is being described for all fifteenpermutations of the four possible features. The fifteen permutationsinclude one permutation with all four possible features, fourpermutations with any three features of the four possible features, sixpermutations with any two features of the four possible features andfour permutations with any one feature of the four possible features.

Although mathematically a set may be an empty set, the term set used inthis disclosure is a nonempty set. Set B is a subset of set A if everyelement of set B is in set A. Although mathematically a set has an emptysubset, a subset of a set is to be interpreted as a non-empty subset inthis disclosure. For example, for set A={subcarrier1, subcarrier2}, thesubsets are {subcarrier1}, {subcarrier2} and {subcarrier1, subcarrier2}.

In this disclosure, the phrase “based on” may be used equally with“based at least on” and what follows “based on” or “based at least on”indicates an example of one of plurality of useful alternatives that maybe used in an embodiment in this disclosure. The phrase “in response to”may be used equally with “in response at least to” and what follows “inresponse to” or “in response at least to” indicates an example of one ofplurality of useful alternatives that may be used in an embodiment inthis disclosure. The phrase “depending on” may be used equally with“depending at least on” and what follows “depending on” or “depending atleast on” indicates an example of one of plurality of usefulalternatives that may be used in an embodiment in this disclosure. Thephrases “employing” and “using” and “employing at least” and “using atleast” may be used equally in this in this disclosure and what follows“employing” or “using” or “employing at least” or “using at least”indicates an example of one of plurality of useful alternatives that maybe used in an embodiment in this disclosure.

The example embodiments disclosed in this disclosure may be implementedusing a modular architecture comprising a plurality of modules. A modulemay be defined in terms of one or more functions and may be connected toone or more other elements and/or modules. A module may be implementedin hardware, software, firmware, one or more biological elements (e.g.,an organic computing device and/or a neurocomputer) and/or a combinationthereof and/or alike. Example implementations of a module may be assoftware code configured to be executed by hardware and/or a modelingand simulation program that may be coupled with hardware. In an example,a module may be implemented using general-purpose or special-purposeprocessors, digital signal processors (DSPs), microprocessors,microcontrollers, application-specific integrated circuits (ASICs),programmable logic devices (PLDs) and/or alike. The hardware may beprogrammed using machine language, assembly language, high-levellanguage (e.g., Python, FORTRAN, C, C++ or the like) and/or alike. In anexample, the function of a module may be achieved by using a combinationof the mentioned implementation methods.

What is claimed is:
 1. A method comprising: receiving, by a wirelessdevice prior to receiving a cell switch medium access control (MAC)control element (CE), configuration parameters of a second cell, whereinthe configuration parameters comprise random access configurationparameters; transmitting at least one measurement report comprisingmeasurement results associated with the second cell; transmitting, basedon the random access configuration parameters, a random access preambleprior to receiving the cell switch MAC CE; receiving the cell switch MACCE indicating switching from a first cell to the second cell; andperforming an uplink transmission on the second cell based on a timingadvance value and in response to receiving the cell switch MAC CE,wherein the timing advance value is determined in response totransmitting the random access preamble.
 2. The method of claim 1,wherein: the first cell is provided by a first base station; the secondcell is provided by a second base station; and the cell switch MAC CEindicates a handover from the first cell of the first base station tothe second cell of the second base station.
 3. The method of claim 1,wherein the first cell and the second cell are provided by the same basestation.
 4. The method of claim 1, wherein the transmitting the randomaccess preamble is in response to receiving a physical downlink controlchannel (PDCCH) order.
 5. The method of claim 1, wherein the timingadvance value is determined based on receiving the timing advance valuevia the first cell.
 6. A wireless device comprising: one or moreprocessors; and memory storing instructions that, when executed by theone or more processors, cause the wireless device to: receive, prior toreceiving a cell switch medium access control (MAC) control element(CE), configuration parameters of a second cell, wherein theconfiguration parameters comprise random access configurationparameters; transmit at least one measurement report comprisingmeasurement results associated with the second cell; transmit, based onthe random access configuration parameters, a random access preambleprior to receiving the cell switch MAC CE; receive the cell switch MACCE indicating switching from a first cell to the second cell; andperform an uplink transmission on the second cell based on a timingadvance value and in response to receiving the cell switch MAC CE,wherein the timing advance value is determined in response totransmitting the random access preamble.
 7. The wireless device of claim6, wherein: the first cell is provided by a first base station; thesecond cell is provided by a second base station; and the cell switchMAC CE indicates a handover from the first cell of the first basestation to the second cell of the second base station.
 8. The wirelessdevice of claim 6, wherein the first cell and the second cell areprovided by the same base station.
 9. The wireless device of claim 6,wherein the transmitting the random access preamble is in response toreceiving a physical downlink control channel (PDCCH) order.
 10. Thewireless device of claim 6, wherein the timing advance value isdetermined based on receiving the timing advance value via the firstcell.
 11. A system comprising: a first base station; and a wirelessdevice comprising: one or more processors; and memory storinginstructions that, when executed by the one or more processors, causethe wireless device to: receive, from the base station prior toreceiving a cell switch medium access control (MAC) control element(CE), configuration parameters of a second cell, wherein theconfiguration parameters comprise random access configurationparameters; transmit at least one measurement report comprisingmeasurement results associated with the second cell; transmit, based onthe random access configuration parameters, a random access preambleprior to receiving the cell switch MAC CE; receive the cell switch MACCE indicating switching from a first cell to the second cell; andperform an uplink transmission on the second cell based on a timingadvance value and in response to receiving the cell switch MAC CE,wherein the timing advance value is determined in response totransmitting the random access preamble.
 12. The system of claim 11,wherein: the first cell is provided by the first base station; thesecond cell is provided by a second base station; and the cell switchMAC CE indicates a handover from the first cell of the first basestation to the second cell of the second base station.
 13. The system ofclaim 11, wherein the first cell and the second cell are provided by thefirst base station.
 14. The system of claim 11, wherein the transmittingthe random access preamble is in response to receiving a physicaldownlink control channel (PDCCH) order.